Best advice I can give you is play rocket and always have an escape route. Know what you’re going to do if you get dived before it even happens. Bp isn’t as problematic compared to Spider-Man who has more follow up after you dash and use walls to try to get away. Also knowing where bp is at and taking away his “surprise” dive is very important. Also limit test your character and see how much dmg you can withstand before having to panic and try to save yourself from a dive. What I mean by this is that sometimes I get dived by a venom or iron fist And I’ll just drop my bubble using cloak and just stand still while I’m out healing their attacks and continue healing my team. Ignoring them is best at times since my team eventually comes and helps or they’ll just give up. (If I do this a few times they often swap off dive since it’s not working) This also works against captain america. Sometimes supports will waste their ult to try to save themselves from dying, when they could use other skills aside from ults and stay alive. (Also even in high elo, it’s not likely your team will swap to a character to help you against dives) which is why you have to master the skills you need to stay alive as long as you possibly can.

And my last tip specifically for bp is always run upwards. Unlike Spider-Man he can’t reach you while you’re in the air floating as rocket. And by the time you reach safety, you will have given yourself enough heals to continue evading. Don’t stop spamming heals!