A thread of loose ends

[Metastachydium]

So the thing is that Thor's proposed method for resolving the matter of the Snarl is quite undramatic. Xykon gets defeated, Redcloak changes sides, and then several weeks of busywork traveling the world and sealing the prison. It's not going to be that simple,

You speak as though you were under the false impression that defeating Xykon and convincing Redcloak to cooperate are one and the same thing, and the latter will follow smoothly andm immediately from the former. The difficulty in getting through to Redcloak is not his loyalty to Xykon, nor is he even guaranteed to switch sides should he become convinced that the Plan cannot succeed, due to Plan B being a thing, and that's ignoring his entire complicated mindset and mindscape.

Further, you are conflating the climax with the denouement. Is defeating Xykon not dramatic? Is getting Redcloak to sublimate his drives into something actually productive not dramatic? If the endgoal of Thor's plan is reached, fixing the world through "several weeks of busywork" will be the compressed epilogue, not the exciting climax.

and if it is that simple then what's the point of complicating the Snarl with the planet within the rifts?

I don't know. What I do know is that it is rather unlikely to be a way to tell the goblinoid subplot to go sit quietly in the corner because it's not important anymore, let alone a means to give us the shiny morale of "segregation was always the answer" as it is often proposed.