Baptiste - low groud
Moira - High ground
Zenyatta - frontline
Ana - your playing ana so wherever you can anti the tank.
Illari - far far in the backline low ground
Brig - in front of the tank
Mercy - backline with pistol out
Annndd yeah that’s how you position your supports.
Ana - Frontline and spam your sleep dart and nade on the enemy tank. Never back down, die if you have to. I’ve seen bad ana players do exactly that (frontline and die trying to nade tanks) it’s hilarious 
Moira - Low ground if your team is playing high ground. High ground if they’re playing low ground. Or don’t play with your team and just dive the enemy backline 
They can’t remove discord if you’re a few feet away at all times.
This one isn’t actually much of a troll option. This helps you hvae people waste mobility options on you, then jump to high ground to avoid the dive or push.
I prefer going with Mercy in the frontline, as close as possible to the enemies.
I can’t believe we left this one out:
Lifeweaver - ALL the way back at your team’s spawnroom door, as not to see the enemy and get scared
Behind the Enemy widow, with Pistol out. 
Kappa
Lucio: Skybox fighting the other Lucio (or someone’s spawn)