hi
first I am not sure if where I picked up this variant rule, so I will not claim it as my own invention...entirely.
it looks like the effect of the Critical wounds is best applied to PCs, who care if the beastman recovers one less fatigue at the end of a restful night? Of that reason my group don`t even bother with activating an action card`s critical effect.
Here is my solution to it.
the Critical card`s Severity Rating now serves as additional Wounds being afflicted upon the monster. I don`t use the text effect at all, only the headline to make some vivid description of the injuries and than apply the Severity Rating as additional Wounds (not damage).
Upon doing so I got an immediate positive response by the players.
by the fact I overlooked it and almost made a complete fool of myself. Afterall I consider myself as a professional GM.