D.va - play behind main tank, keep matrix for other frozen targets
Zarya - bubble frozen friendlies, engage with high charge use bubble just before being frozen,
Hog, turn 180 and run. Or just play behind sheild.
Orisa - use fortify just before being frozen, either back up out of range or focus down with team depending on both teams position in the fight
Ball - engage with enemies not with the mei
Rein - shield towards the mei, let your team do the work. If walled, sheild until the mei comes to your face, and them charge, best youll do is trade.
Sigma, simmilar to rein, stutter sheild back, knock her away with rock, but if youre out of position, you die
Winston - engage on enemies not with the mei, dont engage with jump, use it to escape over mei wall. Use bubble to block meis beam, use both layers of bubble before jumping. In primal, just avoid her.
It really isnt that hard, just stay with your team and dont make stupid positional mistakes.