I'm team "slot your attacks early" to counteract the enemies' rising health. Especially now that we can use SOs so early, they make a big difference. (And I also throw in some useful IOs, here's an example of my Tank at level 15:)
I'm a big fan of knockdown as mitigation. If a set doesn't have kb/kd, I'll add it where possible with IOs (Avalanche, Kinetic Combat, etc.) It also just gives attacks a more powerful feel, more "super".
I'd just like to see Damage enhancement worked into more sets, so you don't (for example) have to choose between a set that adds Damage or a set that increases Hold duration. There should be a set that does both.
My Super Strength for Scrappers:
Punch
Haymaker
Smash (cone attack, Energy Transfer animation)
Build Up
KO Blow (or different name, should be weaker version)
Confront
Handclap
Hurl
Footstomp
If you really want to add more AoE damage to Super Strength- instead of Handclap I'd make Hurl a Ranged AoE, just because it looks weird throwing a big rock into a crowd and only hitting one guy.
Assault Hybrid gives a passive +10% damage. Split the Might of the Tanker IOs into three pairs and that's another +12%. Four purples in Laser Eyes Beams gives another +4%. Not saying this is ideal but it all starts to add up and make a noticeable difference.
With Invulnerability, all five Resist powers are available by level 12, and now that we can use SOs early they give you some good resist numbers. Put the +Def IOs in the passives for an extra defensive boost.
Honestly though, since this game began one of the best early defense powers for me has been Air Superiority. It reliably keeps Bosses off their feet so a lot less damage is incoming.
My suggestion is just to create a separate "Might Melee" set that doesn't have Rage and can be ported to Scrappers/Stalkers. No changes to Super Strength so no one can complain (but they would anyway.)
I find one stack of Rage to be enough, especially with the Gaussian's Build-Up in Invincibility going off all the time. A Rage crash every minute would be super annoying, and I can see why people are complaining if that's what you're doing.
Invulnerability can handle the -Def well but if you're worried, hit Handclap and most enemies around you spend the drop getting up from the ground or stunned.
The -Damage is no fun but at least the Judgement powers work once you're Incarnate. Otherwise you can use the hit to Taunt and maybe re-position.
It's a free slot. If I don't take Unstoppable, I have to use up a slot from somewhere else for the +Def IO. On my builds, I'm squeezed for slots but not powers, so it's an easy choice.