You cant blame your consumer for your system faliure, if you are not making tanks and healers enticing to play thats the DESIGNER FAULT, you cant blame your players for that. Its not even to drag dps to try tanking, is that tanks and healers are saying "screw this crap" and going to dps jobs instead because they are tired and bored of such jobs because those roles became a chore (someone must do it no matter how crappy they are)

If you sell a chocolate that tastes like feet, you cant say "its the consumer fault for having such a delicate palate!"