The paladin forums used to be constant spec bashing. In the distant past it was holy bashing ret (back then prot didn't even count as a spec). Then they both got buffed through the roof and holy got nerfed. It responded by being even more elitist, but with whining mixed in. Now holy just cries a lot while prot and ret take turns telling each other how great they are.
The warlock forums seemed to be great. People were constantly theorycrafting, especially working out incinerate vs. shadowbolt. There was a consant stream of trolls, but people worked together against them. It seemed like they understood that they were all warlocks and they were all in it together. Also they are funny.
The warrior forums are either various forms of crying over there being other useful tanks, arms warriors bashing fury, or warglaive chatter. Almost everyone seems to be a stuck up asshole. Specs and gear are flamed, but no alternatives are given. I think their problem comes from being the only tanks, and therefore the most important class around, for about two years. Now they have to deal with being like everyone else. Very few adapated. The rest either turned into bitter douchebags "Blizzard, we are warriors, no one should be allowed to tank like us because we are a pure class! We should have DPS like rogues too though" or lost all touch with reality "without an interrupt paladins and druids cannot tank, ever. Non-warrior tanks will cause the raid to wipe and all gear to be deleted."
 I don't know why, but all the spaces after periods aren't showing up. That makes this a pain to try to read.