Just a curious thought I had of late. with the number of heroes now in a lucky or unlucky game you can get a hard to beat stack as well as the enemy. More than one occasion I encounter just two Orissas making a bubble fort around a bastion or torb and then theres no really getting close to them and the game is a drag for the whole match.
Maybe mystery heroes should randomly swap you to one of the unplayed heroes that isnt on the feild on death so theres no op stacks.
I know they are adding that all heroes a swapped between rounds but that doesnt help much for payload or 2cp maps