In comp i play Zarya, Dva, Ana, Zen, Moira, Mercy (Lucio and Baptiste more rarely)
Depending on whats needed.
I don’t really know which to call my main, i feel like I main all of them.
Is that too much? Should i tone it down and focus on less? (i love all of them)
Rank: Plat
I would like to climb out of it, although I’m not in a hurry.
Note: I’ve been playing the game since late 2017, so i’m not new and have alot of hours on al of them.
Plat here too.
Depends on the person. I prefer to main 1 hero from each category (dps/tank/supp) and have 1-2 heroes as off mains, having a pool of around 6 heroes. This is my flex plan.
If you believe you get value from your played heroes, keep playing them. If not, shorten your roster to 2 heroes per category. Have fun!
Focus on improving on 3 heroes max at a time seems to be what I generally hear.
I think you actually asked a better question than me. How many heroes should a player have in his pool in general?
Interesting question.
Imo, someone should have a main role and be able to play at least decently the rest 2 roles.
E.g. a dps player should main 1 dps and be decent in 1-2 more dps heroes. In the same time he should know 1 tank and 1 support at least.
So, 1 (or 2) mains and 2 to 4 flex heroes is what I see as optimal, 3-6 hero pool seems great by my standards.
Take my opinion with a grain of salt though, because im somewhat against one tricking. I believe never swapping a hero no matter what will hurt someone’s climbing. Swapping sometimes will make a climb much smoother.
don’t forget, this game has a decent number of one tricks of all heroes and all ranks. the best of them know how to use their hero in a variety of situations to get value out of different parts of their kit.
mercy, for example, can work well in a 1/4/1 comp (4 dps) because that comp lets her mobility feel almost OP, though she uses damage boost less often because she’s spending a lot of her time healing. meanwhile, she’s also been seen in triple healer in OWL alongside ana and brig, where her healing is not needed so she’s getting massive value out of damage boost.
basically, flexibility is important - whether that’s flexible within a single hero, within a single role, or across the entire roster of heroes, it doesn’t really matter. play what you’re comfortable with and what you enjoy, there’s not really a wrong answer 
Plat, peak of something like, 2600 this season
I play 12 to 13 Hero’s, with 10 of those being played very well.
Just depends on your playstyle, your ability to grasp different heros quickly, etc.
Like for me, i can go from every single support hero without needing to warm up. It comes naturally via so many hours put into this game. I can go from Brig to Zen to Ana to Baptiste, with virtually no downtime.
But my friend needs to warm up on one hero, to practice aim, position, ult usage, etc.
I would say, just practice on knowing where you stand; do you feel like you need to warm up on a few heros? or does it come naturally with hours of practice?
I am comfortable with any hero except for Rein on diamond level. I tend to tilt with heroes I find extremely boring to play as well such as Moira, Brig and Reaper.
There’s a few more heroes like D.Va, HoG, Orisa and Mercy that I do enjoy playing however only every now and then, if I would be stuck on one of those for more then 1-2 games it also would result in me falling asleep.