Not me, I'd usually rather join a fresh run. If the [my role] ditched, there's probably a reason and only a 33% (it was either a dps, the tank, or the healer) chance the cause was my predecessor. WP 1/3 could mean a giant tonberry gibbed them (it happens) or it could mean the group doesn't have the intelligence to down the second boss. I'm a relic tank, I do some dps, but not likely enough to kill the adds if the group couldn't.
Wait, what? I'm one of the tanks that queues and takes what pops. I don't bottleneck you guys with repeatedly canceling and I'm an elitist jerk? I really think you need to reconsider your perspective.
I also didn't nail it to just tanks, I play healers too, and most times when I join a group in progress on healer (I don't mind doing it on a tank, I hate doing it on a healer), I find out the tank can't . . . tank or he's level 50 and hasn't figured out the benefit of marking one target, and even if he's spamming flash.