Mercy is very ‘maybe’.
It’s hard to run from Tracer because her mobility can lap Mercy and her minimal falloff can tear her up from quite a a long distance so it’s hard,
I say go Brigitte and play defensively, stay with your ana and make sure you peel for her lots and lots. When I play Brigitte I am very supportive and I will constantly Ben using armour pack once it’s off cooldown. I always armour pack our supports if no one need it just Incase…
Playing Brigitte offensively is dumb, she is a support. But then again I still managed to contest the payload on Hollywood for a solid minute and survived a nano boosted reaper and 4 other enemies so I call it a success.