A Mastermind won't be doing any damage to any target that has any common sense.
In a team environment, Masterminds are irrelevant outside of target saturation to confuse "TAB" tageters, but when there are dedicated target callers on a team that becomes moot. Masterminds aren't putting out damage that is relevant, that is, contributing to a team spike that can't be outhealed or Jaunted away from - they're getting in some annoying disruption that may or may not support team play at most.
In a zone environment, who cares just go the other direction and let the Mastermind do nothing.