Sure, there are ways to combat it, but at 70 pearls, it is both too cheap for its effects and too difficult for non-Astral mages to dispel. In my experience, not only Ermor but also Jotunheim and even R'yleh cast it like mad, which ends in every time I dispel it (at absurd cost) it gets cast again right off by the same nation.
I think it is a rather overpowered spell. It should be a super-expensive hard to get spell, but it isn't.