3on3 you really had mana problems, because you were like 75% cced and couldn't heal mana efficient inbetween cc chains. Still the same in 5.2. But then again why would you play MW in 3on3. It's not that you can't achieve a decent rating, but you have to basically outplay the enemy team every time to win. And with how the game evolved (just spamming ccs and cds) there is not as much room as there used to be. So you can just flat out add around 200 rating if your team played with any other healer.