I would of normally said EeveeA as your Mercy god but it looks like he is struggling in Platinum as EeveeD...Not sure how the other A-C accounts are doing but from what I watched on his stream (a little bit) he is hard struggling...
EvilToaster's stream on Twitch for Orisa, Niandra on YouTube for Mercy, Cloneman16 on Twitch for Reinhardt, and for Roadhog I'm not really sure, Canasian comes to mind but he's a Zarya guy.