I have a proposal:
What if ALL effects could only be triggered x3 times per phase as a maximum? When a card is nerfed, that is (almost) always the restriction they place.
So I am saying x3 times per phase per card. So you could stand two different killer of the wounded three times each.
The advantage would be to allow new cards with more dramatic effects with less risk of infinite combo problems.
This would be consistent with the draw cap and many other x3 only symmetrys in the game (number of challenges) .