I doubt that, i think it has more to do with Tanks gearing up faster through LF content, and generally having to work harder anytime DPS screw up, if they fail at CCing, the tanks and the healers have to take care of it, If they fail at interupting or offensively dispelling its the tank who takes it to the face. the majority of DPS do not want to learn, and woe betide any tank who trys to tell them to do something differently, like asking for a tricks/MD or to turn Growl off. It's like trying to compete in a three legged race where your partner has no interest in standing up let alone being a team player. I'd rather not experience that.
"Every voice matters."I disagree with you a little about tank shortage. I think it is almost entirely because tanks have a lot of responsibility to set the pace of things, know the boss mechanics and often even have to explain them to others.