These have been fixed.
There is couple problems:
Critical hit BUG with cold table
Critical hit BUG with holy table
I believe if this were the case, combat xp would skyrocket. We'll be reviewing xp rate gain at some point in the near future I'm sure, so it's on the agenda for the next admin meeting.
Also, it would be great if I get good XP for severing crits. Suppose, if I severed NPC head I would consider it as IK and get as much XP if that was SQUISH, for example.
This could be done, but there are a number of difficulties with it. For instance, if a combatant has already lost one hand, and you get a critical to remove two hands, should that critical happen or not? If a critical has multiple effects (stunning as well as limb loss) but the text given in combat references only the limb loss, should the critical happen or not? I'm sure there are others, and I feel it would be unwise to open this as a can of worms. In light of these facts, I would prefer to call this not a bug, but a "feature" (however poorly it sits with my desire for continuity).
There is no critical filter. So, if NPC has no hands anymore, you still get singing critial that should blow off mob hands. Either do not let it happens anymore, or just do not show it (like no critical was happen at all).