Redcloak is at least LISTENING to the offer, and didn't discount right out-of-hand the idea of sealing the snarl away forever, he just thought it was impossible.
Also, Redcloak seems rather disturbed that Durkon got his mission DIRECTLY from Thor, while Redcloak has been the High Priest of The Dark One for 35 years and has yet to directly speak to TDO.
Having a Dwarf apparently coming DIRECTLY from Thor, who bluntly knows what Redcloak is trying to do, offering a way to eliminate the threat of the Snarl forever, but ONLY with his help. . .
. . .I think it's safe to say the only way Redcloak and TDO will ever go along with this is if TDO gets many or most of his demands for a fairer deal for Goblinoids in the world, but if that's the price of ending the eternal cycle of destruction and creation that the Snarl has created, I think there may well be another Godsmoot in the making to approve such a deal.