Now add in its RTS roots - an overhead God's eye view lets you watch your teammates. RPG elements means a bad player isn't merely useless, but he's actually feeding power to your opponents.
So a long game, with a prolonged endgame that often results in 10+ minutes of moribund gameplay after the match is prettymuch already decided, without even the dignity of a quick execution like an rts generally provides. No leaving allowed, either. And you get to watch your teammate (you only have 4) who brought this fate on your head, and you're stuck together for the whole round.
They couldn't have designed a game that makes you hate your weakest teammate more if they tried.