I got it working by animating the joints themselves, however the arm is flickering as it moves. I gave your method a shot Warheart but it didn't quite work. Not sure what the issue is with the file. What I ended up doing to get it to the point it's at now is I exported the controls and the joints separate and gave the…
the flickering is probably the joint flipping I mentioned - you'll see spikes in rotation curves for the joints in question. theres a few scripts floating about that reckon they fix it - try swithcing to TCB controlers and reimporting onto the same skeleton though - you might get lucky