It might sound dumb but you weapon accuracy is to high, if you notice everyone tends to have around 35% that is because they are spamming their right click a lot, that is what should happen, also don't die so much and get me kills, mei is an anti tank hero so freeze tanks but don't worry about them let your team while you get the supports, flank more me be crafty , all of mei's skill comes in game sense and making quick right decisions