to add. I found that distance weapons are priceless when fighting the major bosses. Mordoc has a health drain attack that will suck you dry while adding to his health. maxing out the multiple range weapon feats (bale arm, etc.) allows you to fire up to 6 range weapons at once for some characters. avoiding his melee attacks and knocking him down with range attacks I have found as successful strategies.

of course, I haven't fought him on Extreme yet.

to beat mordoc in the second battle you must first destroy the black mordoc or the white mordoc will continue to heal himself or block. There are three strategies you must use, first destroy the black onyx mordoc then dodge the black smoke that the white mordoc shoots out, jump over it, and get behind him and let him have it. finally run. The run in a loop doesn 't work well with him because of his blocking ability. It will work for a time but should only be used to set up your other moves. keep killing the black onyx mordoc attack the white mordoc when he's recharging, when he shoots the smoke,jump over it, and when he reforms after being the bats. You can get good licks on him when he jumps if you block then hit. All his move have a pause that's when you strike. Finally u must have armor with some 60 to 80 stun reductionand ignore knock back or he will stun and kill u every time.

I have fought him on all 4 difficuties. I used the ranged crossbow with +5 lightning and poisin. I had +5 mitheral armour. I would recommend you get these items before facing him. Once you fight him use ice moves or slow that way he dose not get close enough to use life drain. Then attack the black form. Then kill the white form.