Like really all the issues with counter picking and or tank being to hard to kill. Will just disappear the moment you start pointing your gun at the DPS or supports.
They will die a lot faster then the tank will, will force the enemy team to have to split resources away from the tank. And will force out big support tools like nade/suzu/lamp seconds into the fight.
This is especially true as tank, where your large health pool, sustain tools/mobility , and or built kill confirm/combo’s. Are really great at killing the smaller heroes.
As d.va you can fly over the zarya and make her half to choice between attempting to deal with you, or the other 4 members of your team.
A d.va also does 65 damage by flying into a target and using melee, then shooting missles which do 198 damage at close range (as in over 250 damage). And you can do this with DM up at the same time, so that cassidy / ana can’t stop you from killing them.
You can 1 tap any dps/support in the game with rien charge, you an also three tap basically any of them with hammer, then instantly follow up a hammer swing with a firestike if you need to niche out more damage through healing. And this to multiple heroes at the same time.
JQ/Hog can just kill combo any support of DPS in the game, and or at the very least pulling them away from their team so they can’t easily escape.
When you have the numbers advantage, it’s alot easier to position and isolate other enemy players. Including the enemy tank. At the same time you can more easily heal through damage, and have less ults you need to manage.
This isn’t particularly hard to understand, the smaller heroes die faster then the tank. A support can only ever be significantly be healed by another support without having to burn a cooldown. If they can heal themselves at all in the case of Zen.