The problem isn't the speed really, just the collision detection and lacks of weapon physics.
A quick fix would be to decrease overhead dmg or discard it altogether, and to remove the ability to block.
If people have an issue with the pike being used alongside other weapons (pike+bec combo) I'd suggest not to increase the slots used for the pike itself, but to instead make more polearms and 2h weapons unsheathable.
When a weapon is unsheathable it really only needs to be 1 or 2 slots; I'd prefer all such flagged weapons to be 1 slot; it is enough to define the item as a primary weapon and significantly limit the effectiveness of equipping additional weapons.
Removal of the longspear's ability to block alongside flagging most polearms and the larger 2h with unsheathable would fix much of the problem.
