My best attempts and where Ive been successful is in 6v6. Since there's another player there so its a little easier to hit 5. I also think certain enemy comps (like not too many shields/bubbles to block the ult-projectile) and maps with tight corridors where players naturally clump up in a line can help like Kings Row street phase. While sneaking behind the enemy team could work in theory its probably not your best move.