Pretty sure most polearmers only use right->left and thrusts.
I'll have a look at left->right, but I think it's more to do with right->left being a tad OP (instant hits, longer range etc), than left->right being outright bad.
I'll also have a look at overhead (that is plain odd).
Hitboxes are tied directly to the animation, it's impossible to change one without affecting the other.
There is a line drawn from the main hand (right), that is the hitbox. By moving the hand, you change where the hitbox is.
Currently 1h thrust and poleswings use a pretty lame tactic to get round sweetspots (2h and 1h swings use it to a lesser extent).
You simply pile on frames at the beginning and end of the swing, therefore the actual swinging part of the animation is sped up and all falls within a damaging section of the sweetspot curve.
I've tried to reduce that (among the main changes), but still keep the animation competitive. (I'm a bit sick of fighting polearmers who abuse the insta hitting nature)