I kind of wonder if 5 man dungeons would be better. More buffs, higher dps, less reliance on individual greatness, less stress on the tank to do fabulous dps while holding threat. Maybe more people would tank if they were less make or break for a group.
Of course, more tank classes would help. Like how hard would it be to make a tank stance for SAM, one that can't be changed once inside an instance? Or doing the same for summoners with their carbuncle. Sure it'd be chaos, but it might be kinda fun, and at least you wouldn't be able to take a nap while waiting for a queue. Food for thought.