I didn't read but a few replies and i'm not sure if this team has been posted, but after charging up some of my backup heroes' ultimates during the first 3-5 rounds (depending on the difficulty of enemy team setup), then I switch to my new main team which consists of Mystic, Chaplain, Old Curse, Death Mage, and Death Knight. If a round goes badly, then I will retreat and probably swap out my Chaplain for someone who has a charged energy bar. Usually a round goes badly because my team didn't do enough damage fast enough, hence the swap out of my Chaplain. This team is the best one I have found (I am level 55 btw). I'm sure this team would work even better at 45 or below.