The professionals do this right inside the modelling/animation software, but they use very expensive software and have more direct control over animation than we get with DBPro.
Personally I'd most likely make my own animation system to handle this. I mean it's fairly easy to make a system that allows you to rotate bones in DBPro, and for an internal system that you don't intend to share it could be very cheap and cheerful. The maths knowledge needed to have interpolated rotations in keyframes is not that scary, but the main benefit is that you could use positioning as well as run of the mill keyframe animation. Like you might have the zombie and player animating in tandem, so you could have the zombie attack the player from different angles, have them wrestle in whatever way you want - then using position and orientation comparisons between the zombie and the player, decide what animation to play when the characters get close enough to each other.
The problem with milkshape is that you can't have animations that involve a character walking around easily, it's usually a case of animating characters as if they were skewered in the middle of the scene - with your own system you could have loops that are basically the same as that - but then also allow these loops to be used in conjunction with other animations, tracking position and orientation of whole characters as well as their bones.
It's not straightforward by any means I know, but this is really the best way I've thought of doing this, and I think about this stuff a lot. There's so much I'd like to do with a home grown animation system that I'll most likely give it a try before long, I'd like to open up avenues for decent fighting games and better character interaction. I think it must be a real tough problem, I mean I've never seen so much as a flicker of this being achieved in 3D in any hobbyist project. It's really something that is the domain of the pro's I think, would be something pretty special to get it working in DBPro.
We're going down... in a spiral to the ground...