One For All would still be useful for that, but it's 5mins cooldown
Well and one for all will really only help you on things that were barely killing you
Still, not useless! Think the only working Tumult Curator strategy we know of is based specifically around One For All, after all (har har)
From what I can read it gives a shield based on max hp. So basically gives you 20% more hp to work with. Sounds like mantra would be better
That means bringing a monk, though- no one wants to do that!