Personally I think that implementing Vengeance system was just plain stupid. Period.
I don't really understand why of all roles tanks must get free AP everytime they are being hit. There is absolutely no logic in that.
Let my healer get free SP each time I'm hit by aoe. For what reason? So I just can top my meters and outdps damage dealers with my smite, with further lols and humiliating.
Back to good old times tanks had to manage their dps/threat by actual clever and skilled playing. Gearing dps stuff, learning to use proper rotations of skills and so on. Nowadays all the tank has to do to get tons of free damage burst is just stand there and receive hits in face. Not that in my raid tanks outdps damage dealers. No. But they are doing 70-80% of damage dealt by damage dealer class. That is just plain stupid. The same idiocy that was with healing of prot pala (and brewmaster nowadays).
I think every role in raid should do only its role, and personally I don't like when another role is doing my work just because of crap game design. Tanks must receive hits in face, healers must heal, damage dealers must deal damage. Period. We already have all this kind of idiocy in WoW PvP, where healers are tanks, tanks are dd, and dd are healers. Please, don't spread this shit in PvE.