I'm on the fence... I greatly enjoyed Rift, and it really broadened my horizons in that game mode. Previously, I always avoided the Spark. Playing Rift repeatedly made me comfortable with being the Runner. Mayhem Iron Banner might broaden them in a new way. On the other hand, it's very unconventional, and it doesn turn the usual Destiny formula on its ear. I'm usually good for a few Mayhem matches, then I'm ready to move on.