Originally I was using version 10.0.6.0, but wondered if the AMD hardware acceleration only worked on the beta version. This is the DVDFab internal log session.
Kic360
0m 01.18s: ATI Stream GPU acceleration for video decoding enabled
0m 01.43s: ATI Stream GPU acceleration for video h264 encoding enabled
The log show, your used amd gpu for decode and encode, it will be not fast.
If your set subtitle from render to remux , it will use ATI Shrink, It will be much fast.