Badger3d wrote: they thought to play Opponent Fails, I probably shouldn’t have allowed that card to stop a wound soak
Technically, no, you shouldn't, but when you only have 3 players, that is a reasonable house rule to allow. Small groups do have a disadvantage regarding game play and interaction attacks. I think your solution was good.
If you want to still allow for that but not let it get abused, you could allow a rule where the group can play Opponent Fails on only one roll that isn't against them in an Act. It lets them save up for this kind of Hail Mary, but they know that's it.