fbx import / export needs revision.
Its totally broken in 4.10. Importing complex skeletons (200-300 bones with animation) takes about 10x as long as with 4.9 and the import with loads of missing keys thus completely breaking animation. I already reported it and its filed as an official bug. I just hope it makes it into the 4.11 release.
At the same time, export from ue4 as fbx doesnt include scale channels. Not sure why that is but it would be cool to have an option at least to enable it manually. But this is not a biggie if the general importer gets fixed.
Bonus thought: Spring controllers probably wouldnt jitter on transform if the global performance was more optimized, so +1 on that.