Skeletal Mesh skinning breaks on Blend per bone?

I have two animations for different types of attacking, each stepping with a different foot forward and rotating the body in opposite directions. The first strike Here and the second here. The idea is that we have strikes that alternate steps with each strike to keep moving. However, not every step will correspond with the same strike that it was animated with. So we set about trying to develop a way of separating the upper body’s strike motion with the lower body’s step in the direction we need for enemies, etc.

We got this far, using a layered blend per bone of the two animations which isolates the step of one attack and the strike for the upper body but this seems to break the skin due largely in part to the rotation of the hips. Simply put the two animations were not designed to work together like they are being implemented, as my animator states, which is understandable.

However with the number of animations already scheduled, we wanted to minimize creating any replicated animations with the alternate step and see if it’s possible to work it out in engine. Is that possible? I’ve seen other animations blended like this in engine with not too much problem, though I understand that our current usage poses some extreme rotations on the hips and spine. Would I have to do an Additive or something to the hips to keep it within a reasonable rotation range? If anyone could point me in the right direction it’d be a huge help.