Honestly, I can win 14/15 maybe. But I need to quit in the middle of an epic battle because the first few battles will have high gear scores and killer frost. That's a horrifying combo. Those are the battles I can't win. EVII level 50 ww600, KF, and Batgirl with 200+ gear score each always kill me. That's the only team that consistently beats me.
Offensively the only time i have lost recently is one time when i faced Krypto Lex, AO Bats, and Shazzam with 300 gear score each. I didn't tap out my strongest player quick enough and he got KO'd and it was all down hill from there. Generally I don't lose, though it does get tricky with the combo i mentioned above when they have a high healing gear on special 1.