The problem is not really the hero.
It’s the design of ARAM which gives everyone 3 choices and the therefore implemented tryhard atmosphere. Why pick something that you don’t master if you can nearly oneshot 3 enemies with one lategame W of Zuljin? Why pick something hard to play when Mephisto lategame ult can potentially kill the complete team?
Of course some heroes are stronger than others, but given the fact you have 15 heroes to chose from it’s clear that you see those heroes over and over again. Blizzard just thought it’s clever to ask Reddit how ARAM should be implemented… The sh*tshow we currently have was the result.