I do not see that a serious injury is all that serious. I mean sure, if you happen to hit that same appendage again, you get extra damage; but, that is VERY seldom. And with called shot not being on the same tree as all of the "injury causing skills", then it becomes even less effective.

It appears to me that the injured person serves no negatives to speed, to hit, damage, etc. - they just have to hope that they don't get hit in the "arm" again.

If you have a serious injury to the leg, you should go down and be at negatives for striking from the ground.

If you have a serious injury to the arm, that arm should go out and you should loose all swings from that arm or all armor for the shield.

Head > negatives to something - maybe "to hit" and "defense"

Torso > Maybe "bleeding"

I dunno, I would just like to see a Serious Injury, be... Serious.