Get a second deck (preferable one that has a different name). Load it up with your Fire Shield and your Fire Prism. Have an Ice wand. Don't put any Damage-Over-Time spells in it (elf, link, heck hound, scald, fire dragon).
Run down to the Bazaar and buy 10+ Fire Prism treasure cards. Fill the sideboard of your second deck with them.
Use this deck whenever you are fighting Fire. Put the Fire Prism on your enemy before any traps. If he has a shield before your put the Fire Prism on him, remove it by using your Ice wand.
If your Fire Prism is taking too long to show up in your deck, discard something you don't need and draw the Fire Prism treasure card and use that.
OMG i know what you mean..i am magus and still cant deafeat him so your definatly not too weak :-) I mean i went in alone 2 (( which isnt smart lol )) but still he is hard..gonna try it with friends lets hope that works