It seems like they're in demand, which might be indicitive of their viability but I couldn't say as I'm not raiding. I haven't geared my warrior at all really, he's picked up like three pieces because BT stuff went a lot farther in this one than BWL or what not went in TBC. The instances in general are ridiculously short, a few of them only take twenty minutes or so because Paladins and Deathknight tanks can sit there and hold mobs effortlessly and you can blast through everything.
The main reason I hadn't attempted to gear my warrior though isn't because of difficulty of finding groups even with "shit gear" by any means because healers and tanks are still hard to come by but they made an ability in the prot tree that wipes the cooldown on shield slam with a proc of devastate or revenge which basically means you can spam shield slam, TC, and throw in one or two of whatever the hell else you want. Made tanking boring, even if people didn't want easy modes. DPS seems like more fun though. The last one I know of as I say who got tweaked was shaman, they seem to be trying to get more viability for hybrids in 25 mans at least.