Hopeling

I think this overstates the case. Both do have the same resist/defense numbers and the same resist cap, sure. They have the same HP cap, but that's only really relevant for /Inv, /Ice, /Regen, and kind of for /Shield and /EA during their t9s. Reaching the cap is hard or impossible for other sets, so in most cases, stalkers have less HP. Stalkers are absolutely the king of controlled crits, and in a team they have the highest crit rate overall. But scrappers do more base damage, so a large part of this just goes to catching up. And if we're counting ATOs, the scrapper has pretty great ones too. Numerically: with a 34% crit rate and 1.0 damage scale, stalkers have effectively a 1.34 damage scale, but only when you're on a team of 8 and they're all nearby. With a 16% crit rate from the Scrapper's Strike ATO and a 1.125 damage scale, scrappers are at 1.305, even solo. And while the Stalker's Guile proc provides a lot of extra crits, so does the Critical Strikes proc. Stalkers get different versions of powersets, and this is sometimes great but sometimes not. Elec/ and /Ice make out like bandits in the port, but DB/ and /WP much less so because they lose key powers. Losing taunt auras can also be frustrating for soloing. And anyway, in this game, "better at everything except AoE damage" is a bit like saying that a car is "better at everything except transportation". AoE damage dominates the meta; for most things in the game, being pretty good at ST and AoE is more useful than being really good at ST and bad at AoE. I think post-i24 stalkers are pretty great and very competitive overall, and certain stalker combinations really shine. But they also have quite a lot of tradeoffs, and some sets that do great on scrappers are much worse for stalkers.

/Fire is a solid set for general use. It's the classic "offense is the best defense" secondary. Blazing Aura, Burn, and Fiery Embrace are still good powers outside of a farming map. Katana and Dark Melee should both pair well. It tends to work better on a brute, for the resist cap and so enemies won't run from Burn, but it's hardly bad if you really want to play a scrapper.

Hovering at 70 fury when fighting only 2-5 guys sounds about right. In a huge crowd, you'll get to more like 80-90, but that's basically one extra red inspiration. It's not transformative.

Absolutely, haha. It compares the Defender's inherent and powersets against the Sentinel's naked damage scale. I mean, I think Sentinels are a bit undertuned, but not that much. It's not obvious from looking at numbers in Mids, but on a single target, sentinel damage is on par with scrappers, including crits. The damage scale is only 0.95, sure - but then you've got -25% resist from Opportunity, which effectively brings it up to 1.1875, slightly above the scrapper's 1.125. Offensive Opportunity's ~10% bonus damage matches the extra damage from crits. Opportunity doesn't have 100% uptime, but it's pretty high, and unlike the scrapper, -res boosts everyone's damage. But since Opportunity is an ST debuff and the Offensive proc is only applied to one target even for AoE powers, that math is way worse outside of AV fights. If that was tweaked a bit - say, your t1 or t2 apply -20% res on every use during Opportunity - then the inherent would feel more useful, the AT would be more competitive, and there would be a clear answer to "what is the Sentinel's role on a team?": target selection. "Target through the Sentinel" would be a useful team strategy that makes you do more damage. And since you're only debuffing one target at a time, it doesn't step on the toes of support sets too much.

I mean, I'm not getting 100 endurance on every use or anything, but it almost always pays for itself, and double and triple procs seem to be pretty common when I'm surrounded. Occasionally I've gone from half to full. Radiation Siphon has a 10s recharge and a 2.23s activation, and the Theft of Essence proc is 3.5 PPM. With a 10ft radius, its Areafactor is 1+0.75*0.15*10=2.125, so with no recharge slotting, the proc chance per target should be (10+2.23)(3.5/60)/2.125=34%. If you slot it to bring the recharge down to 6s, that's (6+2.23)(3.5/60)/2.125=23%. These are per target, so with 10+ targets, multiple procs should be the norm.

You can't find it in the archives because /Atomic never made it to live. I don't see any reason it should be bad though.

It's an ST melee attack, which heals if the target is contaminated. Sure, okay. All tanker ST attacks are listed as AoEs due to Gauntlet, sure, okay. Target cap is 5, radius depends on the power. But Radiation Siphon is a 10-foot-radius, 16-target (???) AoE. I put Theft of Essence in it and it singlehandedly solved my endurance problems because it procs multiple times on every use. Does it taunt 16 targets? Is the siphon effect somehow hitting other enemies?

It's fine, but its main perk is endurance, which /Ice probably already has handled. Unless you really want laser eyes, you'd probably get more mileage out of something else. Ice Storm is fun if you want to stick to theme. Soul Mastery is good for single-target damage with Gloom. Mu has the best AoE with Ball Lightning and Chain Fences.

OK, so the Gamma Boost entry says that it gives a bonus of (105-hp%) to regeneration... AND to recovery? Am I reading that right? Because that's the opposite of how the recovery scaling should go, no?

I took the question to be about an early low-budget IO build, rather than "should my /fire scrapper take Tough or Maneuvers at level 22?" I agree that for the latter, Tough will give better results.

Is City of Data even still around? I can't seem to find it.

I have not found this to be true. For example, getting my /Fire stalker to a reasonable level of S/L defense (way short of the softcap, and for a fraction of the budget of a level 50 build) paid off far more than extra resists did. You'd think it should work the way you say, due to the increasing returns on defensive stats. But defensive set bonuses are available in larger quantities, relatively speaking: since enemy tohit is 50% base, defense is point-for-point twice as good as resistance. Kinetic Combat gives +3.75% S/L defense for four pieces and can be had at a reasonable price, but there are no sets that give +7.5% S/L resist. Also, even a moderate amount of defense gives you the option to pop 1-2 Lucks and be invincible for 60 seconds, while popping oranges is much less effective and rapidly runs into the resist cap.

In Pine's, Gamma Boost doesn't give any regen or recovery at all, I guess because they weren't sure how to include its health scaling effect. Slots can't increase it because there is no effect to increase. I would be surprised if slotting actually does nothing in-game, but I haven't played /Rad so I cannot directly confirm.

None of this quite addresses OP's question, I think: which should you build for first, for an existing character whose powersets are already set in stone? The answer to this is much simpler: defense always. If you've got a defense-based secondary, get to the softcap, because that's where your secondary will start to feel "complete". If you've got a resist-based secondary, also build for defense first, because layered defenses are great and purple inspirations exist. For what it's worth, this is a lot less true now than it was before i24. I mean, it's still true, but it used to be "you can get maybe a few percent more resist outside of what you get from your secondary and Tough, if you use weird slotting and spend 2 billion inf on this PvP IO", and now it's "your /Shield scrapper can have capped S/L resist without really sacrificing anything". For that matter, building for defense and for resistance often come from the same sets, so they're not mutually exclusive.

It's the -def. If you're at the softcap, -20% unresistable increases incoming damage by a factor of 5.

It detoggles because it gives a -tohit debuff to nearby enemies, and all other-affecting toggles turn off when you get mezzed.

For a very simple change that affects every set equally: rather than -20% def, give a resistable -res debuff. If it's supposed to be "equal" to -20% def, you'd go for -40% res, but the numbers are negotiable. The mathematics of resistable -res mean that everyone, regardless of secondary, will take 40% more damage during the crash. Inv/ tankers go from 90% to 86%, SR tankers go from 0% to -40%, either way they're taking two-fifths more damage than outside the crash. Ta-da: a defensive penalty that affects everyone proportionally. Maybe this has already been suggested, not sure. I only skimmed the first 22 pages. I've also been thinking about Rage as a timed toggle. If it's a toggle, it doesn't even need an End crash at the end; just make the toggle cost endurance. For a timed toggle, a 10s cooldown is just an annoyance: it's still on basically all the time, you just have to remember to click on it periodically. For a change like this, IMO either it should be a normal toggle which you can run as long as you want but has a downside like -res, OR it should have no defensive penalty but work Hybrid-style, with eg 2 minutes on and then 2 minutes recharge (enhanceable) and maybe a crash.

There's "double-stacking" as in having 2 stacks of Rage up all the time, which was only really a thing for very high-end builds, and then there's "double-stacking" as in getting its recharge down to about 115 seconds so that you already have a new Rage buff up shortly before the old one expires. That second option was much easier, requiring only a tiny bit of global recharge bonuses. If you used IOs at all, you were probably doing it by accident. You can see the "Delayed -DEF" on Rage's power entry here, which predates Homecoming. I don't think there was ever a way to avoid the -damage; I distinctly remember giving up on SS because I hated dealing with the damage crash every 120 seconds, even though my SS/WP definitely had enough recharge for the stacking trick. Specifically, the first red response is here, in case you don't want to read all 22 pages. I'm not sure yet if there are more dev posts.

Some melee AoEs do more damage because they have smaller areas and/or longer recharge than most ranged AoEs, yes. Hitting more targets more often tends to make up for it though.

Uhhh...

They do vary widely, but so do the rest of the sets, so that's OK. I feel like most t9s except the crashing ones are in a pretty good place. /WP and /Shield's are kind of devalued for scrappers now that those sets can cap S/L resist via IOs, but that's kind of an exotic concern. The ones with a complete end crash and/or hp crash are barely worth using even when you can fit them into a build. I'd love to see more t9s that have a short duration and a small or no crash; if Unstoppable lasted 45s and had no crash, I'd be all over it even if the recharge stayed at 1000s base.

Sentinels do the expected amount of damage for the powers they're using and for their AT modifier of 0.9, so they deal 80% as much base damage as Blasters, and 120% as much as Corruptors. Dealing ~100-150 damage per cast with a slotted AoE attack is pretty normal for any AT. The Blaster version of Umbral Torrent deals 60.06 damage base, which is about 120 with slotting. For a Sentinel, that's 48.05 base, or about 95 with slotting. In practice, that's going to be a bit more for both ATs due to Defiance and Opportunity respectively, but still within that ~100-150 range.

SS should indeed do more damage for scrappers than it does for brutes, for the same reason every other set should. The issue is that in a straight port, it not only would do more damage than an SS brute, it would do more damage than most or all other scrapper sets, because of the differences in damage buff scaling. You know, it shouldn't be too hard to mock up a DPS spreadsheet entry for scrapper SS, right? Then at least we'd have some concrete numbers to work with.

Because I've ALREADY leveled these characters to 50 the normal way, and I'm already leveling four more characters the normal way, and there's only so much stuff to do 1-20 before I want to do something else for a while. Also, some of my favorite content is at 50.

It's worth noting that -hp is mathematically equivalent to -res. If you reduce an AV's resistance by 10%, that means you can defeat it with 10% fewer attacks. If you reduce its HP by 10%, same outcome. Degenerative's -hp certainly isn't transformative; generally I lean toward the DoT interface procs over the debuff procs. But it's no worse than Reactive's -res, and one of the strongest of the debuff procs.