The divine part is what causes it to get by fire resitance. The warmage gets "Flame Strike" not "Firespell that operates like flamestrike's 50% fire resitance ignore"
Flame Strike
Evocation [Fire]
Level: Clr 5, Drd 4, Sun 5, War 5Components: V, S, DF Casting Time: 1 standard action Range: Medium (100 ft. + 10 ft./level) Area: Cylinder (10-ft. radius, 40 ft. high) Duration: Instantaneous Saving Throw: Reflex half Spell Resistance: Yes
A flame strike produces a vertical column of divine fire roaring downward. The spell deals 1d6 points of damage per caster level (maximum 15d6). Half the damage is fire damage, but the other half results directly from divine power and is therefore not subject to being reduced by resistance to fire-based attacks.