Quote Originally Posted by ijuakos_xqwzts View Post
One creature. Three tanks.
Just want to point out that until I got to this part, I had no clue you were specifically talking about in Alliance raids. Clears up the earlier comment about healers having "visibility into other groups" as well (though I'd say it's still pretty easy for healers to get bored and feel useless in Alliance Raids with how easy it can be to keep a half-decent group alive.)

It's a pretty important detail that makes the post confusing otherwise, though I will add that a fair number of non-high end Normal Raids and Trials have this issue as well, where the off-tank simply has nothing to do besides damage rotation and the rare add phase.

Mechanics that force tanks to rotate, like how tankbusters (more frequently seen in high-end) can give vulns that force a tankswap, are a potential solution to the problem you're seeing. Though every boss doing that would likely not be very interesting after seeing it for the N-th time.