Secondary Powerset: Super Reflexes
High Healing, High Defense, Low Resistance, Medium Clickyness
20% Global Recharge Reduction, 60% Perception Bonus, High Max Endurance Increase, Medium Recovery Bonus, Medium Movement Speed Bonus, Only Positional Defense, No Protection vs. Fear or Terrorize
Sentinel does well with defense due to a low starting HP and having only the standard resistance caps; Super Reflexes is the ur-example of a defense set. It's no surprise that it does well here. What is a surprise, however, is just how well it does. Every Sentinel powerset has an endurance management tool, so Super Reflexes got one added as a rider to one of its autos; they also received an either/or choice for their traditional mez protection of Practiced Brawler, or the all-around much better Master Brawler, which makes Focused Fighting and Focused Senses grant the traditional mez protections and grants Super Reflexes a fast recharging click-absorb that works better the lower health you are. While you'll want to be refreshing that absorb relatively often, it won't kill you to put it off until later,
All combined, Super Reflexes is a powerful Sentinel set that doesn't ever demand your attention in a counter-intuitive way; when you're naturally focused on your health, so is Super Reflexes. When you don't care, Super Reflexes doesn't care either. This set is highly recommended for everyone, from beginner to master.
Take SR powers pretty much at the first opportunity, as you get each of them -- they are so good this is more important than even taking an attack at the same level in most cases, beginning at level 10. The auto powers, for example, give a lot smaller of a defense bonus than the toggles -- but they cost no endurance and they grant you a large and progressively increasing amount of resistance as you lose health, making the back half of your health bar a lot tougher than the front half.
Don't slot Super Reflexes aggressively, you always want to put more focus on slotting your attacks at the beginning. Just make sure you take Master Brawler, not Practiced Brawler.1 You won't die if you take Practiced Brawler, but it's a bad idea.2
Master Brawler's heal is better the higher your endurance and the lower your health, so slotting to keep up your endurance is vital if you plan on tackling tougher content. At low health and high endurance, Master Brawler can give you half your health bar in absorb; at high health and low endurance, it will barely give you anything at all. At least initially, you should save Master Brawler for when you start taking damage, I'd say when you're at 60% or less, but as you reduce recharge to the 30 second or less range, you can start using Master Brawler pre-emptively for tough fights. What's more, since Master Brawler is an absorb rather than a heal, it allows you to preserve the strength of your scaling resistances in your auto powers. In many ways, you are safer at half-health with an absorb shield than you are at full health with an absorb shield of the same strength.
Master Brawler is even so good that it improves your life even when you've been exemplared before its level; if you move Master Brawler to a later position on a respec, Focused Fighting and Focused Senses still retain its benefits even while Master Brawler itself is grayed out.
Finally, although Super Reflexes has a lot of new survivability tools, you're still a defense-based set with ranged attack powers. Don't tempt fate unnecessarily and try to fight from range whenever you can, it will reduce your incoming damage by more than any amount of resistance can do for you.
Panacea: Chance for +HP/+End is pricey at 7 to 10 million influence, but can be slotted in your Health power beginning at level 7; Performance Shift: Chance for Endurance is a bit cheaper at 4 million, beginning at level 17. Both of these are standard recommended IOs for any build, but they take on special importance for Super Reflexes Sentinels thanks to how Master Brawler scales with your Endurance. Preventive Medicine: Chance for Absorb also begins at level 17, and while it's also a standard recommendation for builds, it takes on special importance for Super Reflexes characters; because it won't activate until you've taken damage already, when the flashing red words "PREVENTIVE MEDICINE" pop on your screen, it's a warning to consider using (your now damage-boosted) click absorb. Like Master Brawler, it also improves the worse your health is, which is fantastic synergy for your auto-scaling resistances.
As far as your basics go for leveling, most of it is straightforward. You don't need to slot toggles for endurance reduction until very late, and you want recharge before you want heal on Master Brawler.
Only one power can really be skipped in Super Reflexes, and as you may have expected, it's the Tier 9 power: Elude. There was a time period when Elude was good -- back when everyone had much less defense, stamina recovery, and movement speed, Elude gave you a few minutes of being an attacking monster, especially since you could afford to detoggle while it was active. But we are not in those days anymore. Now, Elude is sadly eclipsed by you just existing. Never take Elude, barring some very, very weird niche builds that are beyond the scope of this guide.
You can put another Performance Shifter in Enduring, and if you want to put any Endurance Modifications into Stamina, put them here first; Enduring is a little stronger than Stamina.
In addition to the choices mentioned above, as is standard you'll want Luck of the Gambler sets in up to five powers over your whole build for another 37.50% global recharge reduction. I try to put +5 boosted Defense/Global Recharge, Defense, and Defense/Endurance in every toggle and auto that gives defense, though I usually end up skipping Defense/Endurance on the autos.
You won't need a lot of IO bonuses to finish capping ranged or AoE defenses; many of your attack slots will offer this. Also of note is Blessing of the Zephyr, which can be slotted into any full travel power. Melee will be slightly harder but not much; Unbreakable Guard is useful in Tough if you took Fighting (I hope you did), and Kinetic Combats are good in a pinch. Try to avoid six-slotting Tactics with Gaussian's Synchronized Fire-Control for the defense bonus, unless you either plan to spend a lot of time in large teams or your primary lacks Aim (just Dual Pistols at time of writing).
If possible, try to go for 48 to 50% in your positionals rather than 45%. This gives you a buffer if you get a little unlucky again an enemy that debuffs defense. If you're feeling up to it, you can try going for 59% to incarnate soft-cap.
Frankenslot for Heal and Recharge in Master Brawler.
While I cannot think of a primary I would not pair with Super Reflexes, its lack of resistances means it's a little better off with sets that have no point-blank AoEs to tempt fate, such as Beam Rifle and Water Blast. Super Reflexes doesn't need heavy slotting, so a lot of primaries will appreciate that. A special note goes to Dual Pistols, which doesn't have Aim and may want to six-slot Tactics with Gaussian's, which grants positional defenses that work well with Super Reflexes (and Ninjitsu). This is addressed more fully in the Leadership section.
For the most part, there's no special synergies for Super Reflexes in Epic Masteries, but Ice Mastery can slightly improve its survivability by putting recharge slows on enemies to reduce the rate at which you're getting hit by attacks. Only helps with extended fights, though.
While all Sentinels benefit from Leadership, Fighting, and Hasten, you may not want to go deeper into Leadership than Maneuvers. SR is a little bit tight on your power choices, and Assault or Tactics may bite into your endurance bar more than you'd like.
Not many incarnate abilities really interact with secondaries, and Super Reflexes is even more agnostic than most.
Destiny: Barrier Core shores up Super Reflexes' only true weakness by giving you a huge burst of Resistance for those times you find yourself forced into close-quarters.
1 If you're curious, the only conceivable situation in which Practiced Brawler is superior to Master Brawler is one in which you are continually being hit by attacks you didn't dodge (like some psionic attacks, especially from Rularuu) and these attacks do not kill you but they do hit you with status effects. This is a very rare situation.
2 And I'll cry if you do it. You monster.