I was talking with gurni some time ago and we discussed the problem with bill/halberd.
The overheads are slow, pretty much anything can spam them, yet they still don't really do that much damage. I don't see why the halberd should have the same cut damage as a katana, or the 1 less than the glaive. Same with the english bills 31p. That's the same as a steel pick and a lot less than the morningstar.
Let the overheads be really slow, hard-to-turn attacks that deals massive damage when it hits. Kinda like the mauls, except instead of CT and backup sideswings, you get long reach.