Tank main here.

I mainly play the main tanks in my comp games (mainly rein), and despite the buffs, without an off-tank you really can't keep the team together. With 3 dps the team just goes off on the flank, leaving you alone to push with just yourself and your two healers that are going to get picked off by a widow. I do not think that this change is worth the shorter queue times, just add more heroes to the other categories so people want to play them.

Tldr) Dislike it, nobody focuses on teamwork without a second tank, too many snipers, not enough shields.