Isn't the fauchard thing a long 4d pole arm?
Yes, but it has laughable cut damage and very high speed, which makes it gay instead of manly.
The problem with such a weapon design is that no matter how slow it is it will hit just as fast as any other weapon if it gets a damage value fitting a long weapon. Warband's balancing logic seems to be that longer means more damage. The problem is that high damage allows hitting early and slow swings are more controllable, making the task of hiltslashing with it even easier than with say a glaive.
Hence why to avoid "slow" weapons ending up being not slow, they should not get good damage.
While it is obviously true that high damage weapons can deal damage earlier, I think you are greatly overstating the issue. Perhaps this is due your tendency to play fully naked, which allows any weapon to nearly insta-hit, however with armour this is less the case. Speed rating trumps damage when it comes to quickness of attacks. A Long Maul is still a very slow weapon, it's hiltslashes are simply nowhere near as fast as a fast lower damage weapon like a Hafted Blade, at least against more than 20 body armour. A Longsword hiltslashes faster than a Great Maul. Besides, I would recommend Glaive range damage anyway for this type of weapon, only then while having like 75-80 speed, being unbalanced, but having 15 more length. Hardly OP, but I so want to play with it.