To me it seems like the problem might be that the 'shaft' of the halberd (blade end) is a couple of millimeters too long, and if it was cut down a little then the shaft would fit into the bottom hand easier. Not 100% sure though. I was also planning to hold both arms on with blu-tac as a dry fit, then glue the hands and two parts of the weapon together while that is held. But my experiment with one has been unsuccessful so far.. They just don't seem to line up very well, which is a shame because as you say the box art seems fine, however, the photos there are not particularly clear. Any tricks you came up with putting them together?
I'm not even thinking about how they might rank up after getting assembled... *Shudder* Overall, very nice looking models but definitely advanced kits.