I'm not too sure that kiting or superior defense will enable a character to actually advance through content, though. They're likely to stall at about the same place and then maybe kill a few regular mobs, but wipe on the first encounter with, say, a Waller or a mob with an enrage timer effect.
You just need to exploit abilities that work regardless of your items. This means CC and damage avoidance. I'd go with demon hunter and kite things. I'm pretty sure there are no encounters where you get cockblocked if you can't kill them in X amount of time, or else people would get fatally stuck there and ragequit the game - and in the end this is still a casual game so it won't happen.
Now that we know that certain enemies have enrage timers going the safe route may not always be a good idea. The ranged characters are still your best bet though if you don't want to depend on gear too much, since evading damage is much easier with them.
well a good weapon is mandatory for all classes. however I think the barbarian is the only one who needs effectively armor to survive. all other classes can evade damage. monk needs gear to be able to dodge effectively to a degree as well making those two the most dependent class. witch doctor can be a mana neutral machine with skills, runes and passives allready without gear and he has pets as well. sorc has free cost spells, but needs crit gear to get to a neutral point for bigger stuff. DH works out of the box as well.
Diamond Skin may become obsolete in Inferno. But the Wizard has several gear-independent skills that, with some clever play, help you avoid damage entirely. That seems extremely important.
Diamond skin acts like an extra health buff IE it only takes damage that would hit your life pool, and according to my messing around with the Diablonut planner that 10853 absorb is just a little bit less then the maximum life I could get in the planner. The max life I hit was ~13K so its an effective hp boost of ~80% when your in end game gear not bad.
Anyway most gear independent class is IMO a pet doctor, as his pets get hps based on his level (means his tankablity stays high even if he naked) and he got soul harvest to make up for any lack of int on his gear (boosts his damage and resistances).
^ TBH you still going to need a good weapon and a lot of priminary stat no matter what class you are.