I had an interesting game last night on Lunar Colony.
This was my first time trying it, but we did the quad tank on attack. It didn't quite worked out, and made question if it would ever really work in comp. based on my sample on 1 game.
First we did it as well as you could expect from 6 random people. We had the right comp, we all went in the same direction together and made it with all 6 to the point...and this is where it fell apart for us.
The first time that went wrong is that unlike OWL where the defending team in up on the right side(looking from attackers point of view), they were defending mostly from the point itself, which is fairly common in gold games. So instead of getting to an empty point and forcing the defenders to take it back. We had to attack a point that was being defended.
The second thing that didn't work out for us is that they had a Bastion and Junkrat. So when we arrived on the point, the damage shredded our shield and was too much for Moira and Lucio to heal through, and we failed.
We made a few more attempts(bad idea) and they pretty much all ended the same way. We simply didn't have the DPS to kill them, once we did manage to grav, well the guy didn't get many in it...and more importantly missed the Mercy who just rez the one we did kill.
It was an interesting attempt, I don't think we executed badly to be honest, it's not a hard strategy to execute really. It's just the way the defending team starts on the point, and different hero(Bastion) selection in gold compared to OWL made it very hard to work.