http://www.omnicmeta.com/p/pc-us-usage.html

mercy is the most picked hero by a huge margin.

followed by dva/winston/lucio.

sorry but days where all you have DPS are over. there are too many support players. its often the opposite. not enough damage because the only people you get are mercy 1 tricks. nothing mechanically about mercy translates to other heroes. so you would have to pray the other 1-3 mercy 1 tricks can actually flex at the acceptable level at GM. most can't.

and before you say "there are more DPS than supports"

people throw a bitch fit the moment any hero is not meta. and seeing how majority of players are bronze-diamond which is like 90-95% of the player base and they BLINDLY follow what pros/streamers do.

there is like what:

genji/tracer on DPS. reaper/soldier sometimes and pharah on koth. and recently added doomfist.

mercy BY A SHIT TON. lucio/ana. and sombra as a support.

so its like what 4-6 DPS heroes and 3-4 supports. and the usual 2 tanks dva/winston.

supports carries games in their own way. carrying a game is not 1v6. its something as simple as proper ultimate timing. or getting a solo kill consistently by yourself. you do not need to be a GM player in diamond games to carry. a diamond is more than capable of carrying a diamond game.