Overworld spawning works just fine but aside when I first load into a planet... no further mobs spawn... the planets are utterly barren except for some set spawns like the villagers on Trenzalore...

that's just a spawn coding error im afraid it's broken 

 Ah okay, so it isn't an imcompatibility issue.

We have no idea what's causing this. To compensate for this, I'm releasing an update later this week where there will be structures with mob spawners on other planets.

Oh im looking forward to it Matt

 Oh that's perfect! Funny enough I had actually cheated in some mob spawners to place them around a few spots just so I could fight the mobs lol, but that's great! Will I have to reset the dimensions though?