Interesting angle on what Odin's objective was here. As Roy mentions, if he actually wanted the world destroyed, he could have just voted "yes". He didn't. If he had not delivered the prophesy, Durkon would not have left the Dwarven lands in the first place, not become vampirized, and thus not returned to force the vote to result in the Dwarves all dying and going to Hel.
Of course, that misses a bigger piece of the puzzle. Redcloak's plan would have gone forward anyway. Without Durkon joining the Order, it's possible that they would have failed to prevent that plan (so far anyway). Of course, the risk there is a sequence of gates being destroyed (just as they have), which puts the Dwarves souls in danger (hence the prophesy). But if he doesn't do this, then the alternative is the Dark One being able to move a gate from the prime material plane to any other plane (like where the gods are). He plans to use this threat to get concessions, but the reality is that this would cause the snarl to cease to be something that just threatens the world of mortals, but now threatens everyone, everywhere. It's been pretty clearly established that the gods were safe on their home planes. Now they would not be.
Which is by far the worse outcome. In order of terribleness:
1. The gods destroy the world to prevent the snarl from escaping and unmaking everyone. Everyone on the world dies, but their souls go to their respective afterlives. And the Dwarves go to Hel. So... bad.
2. The gods don't destroy the world. The last gate is destroyed and the snarl escapes and unmakes everyone. Worse.
3. The Dark One succeeds, and shifts the gate to other planes. The snarl proceeds to eat the gods if they don't do what DO wants. Much worse.
4. The Dark One succeeds, and shifts the gate to other planes. Turns out he can't control the snarl, and once released in any fashion, it proceeds to eat the gods, and no longer stuck on one plane, proceeds to go on a muti-planar eating spree. Everyone and everything is unmade, everywhere. Not just "worse", but literally "the end".
Odin may not be acting like a jerk here, but taking a risky action that provides the best chance of avoiding that worst case scenario. Heck. It's entirely possible that he lied about what would actually happen, knowing that this lie would set in motion a series of events that will result in things "almost" going sideways, but turning out ok in the end.
From a meta storytelling point of view, it's clear that the gods aren't actually going to unmake the world, so Hel's plan will be foiled somehow (kinda got a whole book left to go here, right?). So the "prophesy" will somehow not be fulfilled (or will be so in a way that doesn't result in that end). But if, along the way, Odin's prophesy set in motion a series of events that allows the OOTS to foil both Xykon and Redcloak's plans, then it was the right call for him to make. At least that's my guess.
The one element that's missing is that the fact of being vampirized and returning home in this manner has to somehow be a key factor to the OOTS succeeding. Otherwise, why bother? Presumably Roy would have found some other willing cleric to join him on his adventures if Durkon hadn't been available (cause he never left the Dwarven lands). So it can't just be "having a decent cleric along for the ride" as the only effect of Odin's prophesy. Something has to come of this entire plot section that has a direct effect on the ultimate conflict between the OOTS and team evil. No clue at all what that may be at this point though.