@feha
1) He is extremely scared. Rational thinking is very hard when in that kind of situation where you are not hit yet, but know anything will kill you, almost at a guarentee.
2) He is an amateur. He has a month of experience. Not years of practice.
3) What if Dismantle does not work? Yes, it cannot be used against everything. He then has put himself into a deadly position for a 0% chance to come out on top.
4) You try getting mauled and dismembered a few times and see how eager you are to get into the same situation. He is not a masochist. He would rather not have to rebuild his body every time he sees another lifeform.
5) This cut out quite a bit. Since acquiring dark magic, he does use it to dismantle enemies. It is his go to for the most part. But it cant always work. Some enemies cant be effected by it, or are simply too hard to make contact with, or there are too many around.
6) If all you know is kill or die, what happens when there is a situation where either outcome is bad? Like in a tournament, or a drunken fight? If all he knows is sure fire kill moves, he is fucked. So getting some practice is necessary. Just in case.