Upon conferring with my teammate Adam here, we originally thought that our issue was the same as OP’s but upon reflection and investigation it seems they are related but not the same. We’ll split our problem out into it’s separate post to allow Peter to focus on his problem here in this thread (gl, Peter!)
[EDIT: For people finding this through web searches and have a problem closer to ours than Peter’s, the new thread is at:
[5.5] Default FBX Interchange importer doesn't import integral value curves ]