It's not just long stabbing weapons, it's long weapons in general. Length is worth too much, especially with all the ganging up that people do. Take the most effective weapons right now and compare their stats to each other. The one thing almost all of them have in common, is length. I don't really think these weapons need a huge nerf, but there is certainly a disparity of effectiveness that is directly related to weapon length, and that is an issue.
Glaive
weapon length: 160
weight: 2.8
difficulty: 16
speed rating: 90
weapon length: 160
thrust damage: 22 pierce
swing damage: 39 cut
Hafted Blade
weapon length: 132
weight: 1.7
difficulty: 13
speed rating: 94
weapon length: 132
thrust damage: 20 pierce
swing damage: 36 cut
Four speed is somehow worth 30 length, 3 cut damage and 2 pierce? Really? I know the hafted blade is just a shitty weapon in general and greatly in need of a buff, but that's a bit excessive.
Danish Greatsword
weapon length: 124
weight: 2.5
difficulty: 15
speed rating: 92
weapon length: 124
thrust damage: 24 pierce
swing damage: 40 cut
Two-Handed Sword
weapon length: 110
weight: 2.2
difficulty: 12
speed rating: 95
weapon length: 110
thrust damage: 22 pierce
swing damage: 38 cut
Three speed for 2 cut and 10 length? No thanks, length, even if it is "only" 10 is way too effective, especially because you have to think about all the people that you're now able to out-range because of that 10 extra length.
As weapons get progressively shorter, the ratio of speed:length and Damage:length needs to be increased as compensation for increased loss in effectiveness due to being so much shorter than the average. It doesn't make sense that 5 length should always translate into x damage. The difference in effectiveness between 150 length and 160 length polearm weapons for example, is rather minimal but the difference between 110 length and a 120 length two-handed weapons, is quite large. The 150 length weapon has a range advantage on almost all of the weapons that the 160 length weapon has, but the 120 length weapon has a range advantage over the majority of the weapons in crpg while the 110 length weapon is only average or slightly above.