Since it only affects armor prot and not skin prot, not only are high natural skinprot creatures like Trolls and Crushers unaffected, but units affected by protection buffs like Wooden Warriors, Marble Warriors or Army of Lead lose only their armor, not the protection provided by the buff. This can be useful either for the Acid Storm caster, or for the opponent.
Assassins, Mind Hunt, remote assassination rituals, flyers, etc. can also be effective counters to Acid Storm depending on who or what is casting it
