I agree with what Largg is saying. For two-directional polearms that aren't geared towards cavalry, is it possible for you to consider either making a separate formule, changing around the item weights, or adding a straight modifier (1.3x for example) at the end of the equation for them?
Here are some values, for the sake of discussion (all values assume weight at +0 heirloom level):
2h:Miaodao: 8.5
Longsword: 10.2
Long Iron Mace: 7.3
German Greatsword: 7.86
Great Axe: 9.32
1h:Liuyedao: 11.72
Military Cleaver: 9.23
Warhammer: 10.85
Italian Sword: 10.82
Broad 1h Battleaxe: 11.87
Polearms:Hafted Blade: 10.62
War Spear: 9.9
Long Hafted Spiked Mace: 7.68
Glaive: 7.16
Poleaxe: 7.56
Long Spear: 4.3 -> 5
I'd say these values look very good so far. However...
2d Polearms:Swiss Halberd: 6.72
Awlpike: 7.5
Corseque: 6.6
English Bill: 4.52 -> 5
Partisan: 6.16
Long Voulge: 5.3
Not a single one of them can even turn as well as a Poleaxe, despite the fact that they're supposed to be geared towards overheads and stabs. Frankly speaking, that's pretty bad. This isn't just me cherry picking examples either; none of the dedicated two-directional polearms, which is to say any of the two-directional polearms that cannot be used on horseback or with a shield, can outturn a Poleaxe. With the addition of a modifier though...
2d Polearms w. 1.3x modifier:Swiss Halberd: 8.74
Awlpike: 9.75
Corseque: 8.58
English Bill: 6.3
Partisan: 8.01
Long Voulge: 6.89
With the exception of the Long Voulge and Bill, I think those are pretty good values relative to other weapons. For those two specifically, you could consider dropping their weight by .5kg for the Long Voulge and 1kg for the Bill to arrive at a turn speed of around 8.1 for both weapons.