So a lot of WoW blogs are loudly complaining about the new Call to Arms system bribing mostly tanks and to a lesser degree healers to join pickup groups. Unsurprisingly the loudest complaints are on blogs that have words like "rogue" in the blog name, with the principal complaint being that it is extremely unlikely that somebody playing a pure dps class will ever get that reward. So the new system has been called an "inverted hybrid tax". I think the complainers are overlooking the fact that dps classes are the principal winners of the new system, as it is *their* queue time that will diminish, not the queue time of the tank or healer; and the justice / valor point rewards from queueing faster are a lot bigger than the bribe Blizzard offers to the tanks.
But let's assume that for some reason you don't want this bribery, or think it won't work. That leaves us with the original problem of not enough tanks queueing up for pickup groups. So how else could that problem be solved? The only reasonable alternative proposal I have found up to now is Rohan's suggestion to make groups require 2 tanks, 2 healers, and 2 dps; thus no role would carry more responsability than the other roles.
Everybody else is just wishing for miracle solutions, without even giving a hint of how those could look like. "Make tanking less stressful" is a goal, not a solution. "Make tanking easier" likewise, because the only thing Blizzard could do would be to make dungeons in general easier, but then dps would just use more AoE and the tank would still be the most stressful role.
The main problem is that it isn't Blizzard who decides who does what. For example why does it have to be the tank who sets the raid marks for kill order and crowd control? Or who explains the other players how an encounter works? In combat the larger responsability of the tank derives from the core of his role, of what "tanking" actually means in terms of aggro control and damage mitigation; but even there it is the players who often attribute responsability badly, like the dps not using /assist and not hitting the mob with the skull icon over its head, and then complaining that the tank isn't holding aggro. What would Blizzard be supposed to do about that?
So if you have any better solution to the tank shortage problem than bribing the tanks, let us know!