Yesterday I've found a quite serious issue that was messing up vr composer (all frames were considered stale because of that). I also changed shaders a bit and they should be easier on GPU. Still LODs have to be added and meshes changed. But I've also found out that there is something really wrong with CPU right now - I am setting up more specific profiling tools to check what's exactly going on there.
There wasn't much going on recently when it comes to performance/gameplay code and I can't still find why 0.3.11 works better. Actually when I investigate it, it works as bad as 0.3.12 :/
There is a discord server (right now I am on my phone, but if you download pc build, ghere is a readme file with a link).