Any person "maining" exclusively one character in Overwatch are kind of doint it wrong, to be honest. No way in hell can you play the game always at optical team comp when you are stuck with one character, so you need to be proficient with at least 2 or 3 of different classes. Not even an expert, just "proficient" is enough.

As a Mercy main, I can only say this. You can go ahead and say that, AFTER you take care of the Winston on my ass.