I have seen a lot of complaints here in the forums about tanks ruining non role queue modes, and while here people complain about everything, this one was legit.
That does not change that having 3 tanks is very optimal. 1 tank can easily duel 1 or even 2 dps who try to flank supports, and 1 tank is more useful diving than a dps character. Then, 1 tank on the frontline protecting the team and pushing/defending point.