I've had good mileage out of using both inferno and dispelling shot and alternating between the two. Personally I favour dispelling shot over shattermantle because I consider it more widely useful - you face far, far more magic-users than magic-resisters. That said, I'd still use dispelling shot on mobs that had no buffs simply for a few extra dmg dice, but my build had spell points to spare.
On the spell point front, getting all the Energy of the Wild enhancements will give you the Magical Training feat, and hence Echoes of Power, which should give just enough top-up spell points to get off another shot even when running on empty. Combining this with the Soul Magic enhancement will make things much easier.