I have already climbed its complete rng you can be 2900 mmr in some lobbies 2500 in others no difference between 1900 lobbies and 2300 lobbies damage does not matter at all healers are too strong for one persons damage to change the pace of a game.
I could quite literally win some games at 2500 mmr from just pressing chains of ice or sitting at a base defending i would love to know what plays you think you have been making to solo carry blitz games it would be interesting.