There's a possibility that Mcgree and D.va could be nerfed in the future.
D.Va is supposed to get buffed. She's currently perceived as too weak.
As for McCree, no surprises there. Great at medium and long range, Flashbang + Fan the Hammer can take out basically anything at close range and FtH -> Combat Roll -> FtH even gives him some considerable tank busting capabilities. That really is a bit much
Some other characters that need looking at, imho, are Symmetra and Widowmaker.
Symmetra... her classification seems strange to me. Feels more like a defensive builder like Torbjörn than a support. Generally, it seems like Mercy and Lucio are the go-to supports, but Symmetra just feels all kinds of wonky.
Widowmaker is hard for me to assess properly as I'm not good enough with her yet, but she feels pretty ridiculous to me. Her range basically allows you to avoid counterplay from most characters, she has great mobility (even in a pinch) and her backup SMG mode for her rifle is surprisingly good (compared to how Hanzo fares once pushed upon, for one) - and then there's her ultimate. Not only is it incredibly valuable to have that wallhack, it's hard for the enemy to notice the activation, it charges quite fast, it's gloabl and
persists through death. I can absolutely see competent Player dominating games with her and good teams revolving around a good Widow like Counterstrike teams revolve around a good AWP guy.
Also Competitive Play could return next month.
Any word on bans in competitive play? Took them ages to implement those in Heroes of the Storm...