It is worth noting that Aron actually isn't 2HKO'd by Life Orb Murkrow with the correct spread. It is even better in Sandstorm.
Speaking of Sandstorm, most rock types are good answers to it when sandstorm is up. Nosepass can take HP Grass, Archen gets a boost too (but evio archen really doesn't do much in my experience.) Even Tirtouga can take an HP Grass in Sandstorm.