simply have the following four items i have found which makes
your weapon hit with a spell called fire strike, and Master Firestone dmg.
FYI:
Oh and it might help to have +Spell damage or you'll be sad when you hit for like 20 fire damage :P
Items:
Master Firestone (You get these from locks)
Blazyfury Medallion (Either your server has a necklace vendor or your kinda in a pickle here cuz this dropped off pre bc kazzak in blasted lands)
Fiery Retributer (Hazza'rah drops it [ZG], or if your server has vendors it will be in 65+ weapon vendor)
Fiery Plate Gauntlets (Blacksmithing Can make this)
Screenie of dmg:
http://img171.imageshack.us/img171/3307/fiaaagk6.jpg
Had 826+Fire spell damage in this pic the shadow bolt damage was from shadow oil.