I would argue that unyielding adversary is VERY useful in pk. (It served me well with Nererial.) A lot of fighting as a shaman is about drawing fights out, and the more efficiently you can use your mana the better. It also means you don't have to keep clear of your enemy for as long each time you break off to heal.

Claim the unfettered can be taken by an orderly shaman. I had it with Nererial, who was Imperial High Priest. I would, however, advise that it's not as great as it sounds. Typically I'd strip something like the +ac bit of a frenzy.