Of adding some -dex or even -hit roll to some abilities. There's almost nothing out there that adds -hit or damage roll. I could see some edges for something like boneshatter, whirl, and so-forth, that add -hit/dam roll, which wouldn't be overpowered.

I like the idea of jab adding some stackable negative dex.

There's an edge for wither to nuke some dexterity. But you're right, shamans need something. Maybe not a revamp. But look at some of the abilities they get and tweak them some.