Yeah, for the hobbiest or the poor film-maker, Rotoscoping is a very legitimate way to go.  Nice thing about Poser is that you can load an animation into the background.

The downside is that you now have to key frame everything yourself and, yes, this can be very time consuming.  The other downside is that your video footage is 2D and when you start moving your camera around to tweak things, your reference is useless.

Still, there is a lot more potential there.  I've got a pretty big project coming up and I've been looking into mocap for a long time.  A big problem I've run into loading up BVH files is that the mocap doesn't always translate joint movements correctly.  A recent test I did resulted in the figure's arms pivoting in an impossible way on the elbow.  Clearly the original actor's arm was twisted, so the action was natural, but the available mocap doesn't differentiate where the bicep and tricep is, for example.

Pretty much every mocap file I've tested would require so much reworking that I'm thinking the rotoscoping approach will be less work!