This is a team problem. Jump in voice chat every game and if nobody’s there, oh well. Eventually someone will be and you will find people who will play as a team. Play a bunch of QP together and get used to each others’ movement and priorities. Sometimes, as a support, you have more vision on the battlefield. The new ping function is great for marking priority targets. I feel more than comfortable playing Mercy with my group and much less so with queued teammates. I know my tank isn’t going to insta-dive Zarya & company at first contact and will be receptive to backing down when I call for it. A lot of times tanks are focused on what’s happening tight in front of them and damage is focused on their current target. Especially as Mercy, you can look around the area without losing healing efficiency on your current target. Ping, call out, help your team position.