I'll give you that druids are OP, but really, I was running with level 70 trinkets on our first 25 man kill of each boss.
I'm gemmed for DEF right now because def gives dodge/block/parry/miss i could take out every def gem and still be fine.
There really are not any higher ilevel enchants for tanks than the def ones, why not use them free up gem slots for other stuff if you want, or go crazy with more def gems like i do.
My pally is gemmed for hit mostly these days... (totally lame of them to remove the prot hit talent when like half of our moves require spell hit)
I dunno, it was just never really a problem for me, crafted gear alone can make you def capped at 80, and while there is a potential for a few "crap I can't equip this until I get..." moments, all classes have that problem (except probably druids), I can't tell you the number of times i've heard mages complain that they can't equip x new thing because it doesn't have hit on it.
It does kinda suck for DKs though since there are no tanking 2handers and they can't wear shields... I just figured they were expected to dual wield tank weapons
I'll probably switch to all stam gems if uludar offers up EHP challenges.