There wasn't one for WoL, I don't have HoTS but I'm pretty sure it doesn't have that (unfortunately). As much as a good idea as that would be, it would make it impossible for Blizzard to see any fair balance issues against different matchups. I think it's better to just let Zerg babies cry and cry until Blizzard realizes they're the ones that need a patch the most by looking at the ladder statistics and seeing an unusually high win rate for Zerg.