Not trying to be an ass....but you said you were bronze. I wouldn't be surprised if they all do need healed 24-7 and babysat. I tried to dmg boost for things like hog hooks, ults, lulls in between massive "battles", and randomly during team fights (as needed). It took me a while to figure out when to do the damage boosting that was best for the team, but once you get it down...it's one of those things you just don't forget.

I have my most time on Mercy, then Moira, then Ana, and finally Zen. Though, if pressed, I'm a mid-plat Brig....I just dislike playing her and am not really good. I tried to make sure that I wasn't a "one trick", and as soon as I branched out from my "main" - I started gaining more SR. It's always nice to have a back-up to play, just in case.