Since Grisban’s ability only activates at the end of his turn, it is useless against Immobilize, and is technically useless against Poison because of his Strength. Weakened is removed by resting, so the ability won’t affect it.
Stun, Burning and Bleeding take an action to discard, so using a rest action to lose them is a bit pointless unless you needed to rest anyways and stun forces you to use your first action anyways.
It would still be good against Cursed, Diseased and Doomed.
It's in the errata. His ability activates as soon as you declare a rest action: you have to wait until the end of your turn to get the fatigue back, but the condition is gone immediately.
I missed that one. But at least, the more expansions we get, the more conditiones there are that he can use his ability against.
Still not as good an ability as most other characters, though.