I’m not certain why they haven’t changed this in over 5 years, but apparently this is still a problem. I get about 2-6% for a win, but I am losing 7% for a loss. It doesn’t matter that I am doing well or have the best stats teamwise (high mitigation and dps as a tank) it seems to want to stop me from achieving something. The only thing it is doing is making me want to quit this game. At this point, I would need at least 15 wins just to rank up from 3-2 and 30 wins to make it to a new rank, but even if I have above a 50% win rate, the amount I’m losing is preventing me from climbing at all. I’ve sat at 9% in rank 3 after 17 games with 9 wins, it’s gone down to 2% but wont climb above 9%. This is a broken system and it’s going to be why I quit this game again. Another 5 year hiatus seems in order. Maybe by the time I’ve come back the developers will all be fired and the game might be worth playing.
Honestly they need to go back to the old system where it was based more off ur skill. I miss doing well and having the potential to double rank up or make a lot of progress or if I did well and lost I wouldn’t lose to much. But now it’s so annoying u win 20% u lose 20% it’s incredibly hard to make any progress now, especially if ur constantly getting 50/50 streaks or mainly loss streaks
You just need to play more. Once it has your rank established you will get about 22% (±3) for a win and lose 22% (±3) for a loss.
on my alt its the opposite, I practise heroes I usually don’t play since the rank reset and it pushes me divisions up even when I lose. 
its also super easy to lose unless I go to my very best hero and only focus on ruining the enemies day without looking what my mates are doing.
which is simply not playing for flanks. I still have very good stats, high kills, low deaths and much uptime. but All I do is fall back once my team got rolled.
Only way to win is going solo behind the enemy lines and getting 1-3 picks before my team arrives at the scene. That does get exhausting quickly.
I wanna practise dumb poke for once lol.