Mercy Players- What do you find annoying?

i find it really annoying when i get left behind to deal with the enemy. For example, i saw a D.Va out of Mech with a roadhod in a room alone, i flew in to keep her alive, she finally got her mech back and instead of killing the roadhog she flew away leaving me to be hooked and killed, this has happened many times with heros such as Phara, Genji and Winstone.