I wouldnt place the blame solely on the RCD for the other dog getting hurt. I have read some of your post about Ruby and it sounded like she was a little on rough side. That could have happened anytime.
In my opinion a dog sold as a started catch dog that has caught a few hogs including a 400lb one (finished cd or not) that will not catch or ESPECIALLY not help catch after a cur catches is a real bad deal and should be frowned up on by everyone on this board. CULL! With that said I know what you mean is it can happen to any hog dog any day, especially a rough one but that is not the case so has no room for discussion because argueing hypothetical points is a waste of time. .02