Oh, okay. In that case, you're right, dominating it wouldn't stop you from being hit.
How about this, then, in order to make it slightly more powerful.
Helm of Fire Dominion Level 21
This powerful helm, crafted for the High King of the Kingdom of Farland in its hey-day, is intricately carved and polished; flames are perpetually reflected in the burgeoned surfaces of the helm even when the wearer is not near fire.
Slot: Head 225,000 gp
Property: Gain resist 10 fire.
Power (Daily): Minor action. Make an attack against a monster with the Fire keyword: Ranged 5/10; +24 vs. Will; on a hit, you dominate the monster until the start of your next turn.