For me, it's maybe about as good as mental jolt -- except you have a pretty good idea from typing 'who pk' which people in your range mental jolt will wreak havoc on and which won't care enough, whereas it's much less trivial to figure out which people in your PK range are wearing 800 pounds of metal armor for some reason.

Not every time, but most of the time the druid has a much better PK choice than telluric surge in my opinion. (And what it is will vary.)