The reciepe on how to kill ANYTHING as a mage (cost a bit of mana though, so only use it when you have problems):
First, curse them (survivors curse, so the can't resist it <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />). When you've taken their res down enought, life leech them (four or five times should do it). Finnish them off with hellspikes. If you don't whant them to be able to do anything back, push in a freeze before the leeching.
Übereil (tnx to Kiya for this tips <img src="/ubbthreads/images/graemlins/wave.gif" alt="" />)