Yeah that is an issue, the current fix is that after 180 seconds of stalemate all healers/supporters will use their ultimate one last time and then enter melee combat (aka "The last march of the dwarves").
Ah, so that's what happened! I also encountered a mob of banner orcs and thought I had to end the game manually because they just kept on healing. Good to know there's a way out and we don't have to abandon our crew.
