Disclaimer: eidt: probably even more broken in 4.11 after a closer inspection. Stuff imports fine (mostly) but material elements are completely messed up.
Im having a really frustrating time with 4.12 fbx importing: Heres a video that decribes the issue.
Here again as text: Ive got a character with roughly 72k triangles in total. Spread over body, hair, eyes, eyelashes, eyebrows, nails, teeth and tongue geos. The skinCluster is fairly heavy as it has around 390 influences in the body. One thing: Due to that it splits the body into two material elements which seems to bug with the other material elements as the next material element will affect two objects that were supposed to have an individual element each. So thats problem number one. I can fix that myself by adding a material buffer object that just contains an empty unused material.
The big problem tho is I cant seem to import the full fbx. It always crashes with different crash reports. If I remove one or two objects from the fbx it works. And it doesnt seem to matter which ones so its not a mesh specific problem.
Id really like to go with 4.12 but as it is now Its not useable for me guys. And that sucks Again: Ive tried this in 4.11 and it worked perfectly fine so something must have broken on the way to 4.12. If you Epic Devs need my .fbx and .ma files please send me a pm and Ill get them to you discretely.
Thanks for any help,
PS Ive also made an answershub question: