The Dark Matter 1 files are fine, except that they are antiquated. I re-rig and reanimate the ones that I want to use. I also find them handy for setting up low poly shadow casting objects for characters (after I've reanimated them).
The workaround for the DM2 models is easy enough - use timer based animation and animate them at a high framerate. It will just skip the 159 extra frames. Or, fix the sync rate and animate them at your desired rate*160. It can still slow down if your framerate dips but it works as well.
The real problem is that the files are 160 times the size they should be. Those extra 159 frames dramatically increase the size of the files. They are low poly. I reanimated the knight with 20 animations and he went from 6 mb to 250k. It dramatically increased performance. In DBP performance has not only to do with polygon counts, but limb count and very importantly file size. They are not suitable for use in a commercial game as they are. But, it's easy enough to fix and the models are good enough.
Come see the WIP!