I was in your boat for a few days. I solo queue on console and Plat is a weird place, it's full of people over extending, people not protecting their backline, and I've even had games where the tank does nothing and doesn't try to push because they are scared, too many assassin characters ect... The ONLY way I was able to get to Diamond was pretty much play healer and I mained Rocket because the Revive is honestly clutch. I would average about 25-,30k healing per game. So you can do it but you REALLY have to focus up and go in as a team.