Honestly, I'm quite clueless how to fix this. Not sure if damage nerf would even help, because long spears would still be able to stun from a mile away (maybe it would help reduce the number of people using long spears, as they wouldn't get so many kills).
I guess immobilize when the attack is chambered would help (someone else suggested this). This way you could still protect archers from cavalry and your team/castle/village from enemy charges - while unable to go kill hunt around.
What's sad is that every 2h/pole picked up a long spear in an organized group fight (Karindi for example).