They do, won 2 last night actually.
The “secret” is to be aggressive and attack Horde first, it goes back to that whole thing about “the best defense is a good offense”.
Commit to a massive first strike, pop all cooldowns, and wipe the enemy team seems to work well for Ally… if, and ONLY if they win the first teamfight.
After the first wipe the momentum actually lasts for a while, since it causes the enemy team to split-rez and trickle out of their base.
That said, I’ve been in a few longer games where we started out strong (took an early lead in points), but as the match progressed and Horde regrouped into a deathball we just got out-killed and ended up losing.