As far as I know, Dispell does not work on Evards. Better luck next time, LJF.
However, as a spell, it DOES have a lot of counters.
1) Wizards/Sorcs/Bards can use Ghostly Visage and nullify a good deal of the damage.
2) Barbarians/Fighters/Rangers/Paladins have full BAB and decent Strength, which makes them more likely to save against it.
3) Rogues can use scrolls of Ghostly Visage
4) All Halflings and Gnomes are automatically immune for being teeny tiny anyway
5) Anyone can pick up a belt to reduce bludgeoning damage, further taking away from the spells effect
Remember that whilst it gains a lot of power if you Empower it, it's also a level 6 spell by then, and in league with Chain Lightning, Circle of Death, and Tensers Transformation, and IGMS to list but a few. Its raw form at level 10-ish is pretty damned feeble, all things considered.