You're not alone with this, I use the pike a lot, love it for doing a nice support *cough* killsteal *cough* role.
(Joking aside, it's a nice weapon if you prefer helping your team, having a guy dedicated to taking out cavalry, and helping you out in tough situations is always good, right?)
But these not-registering hits are very common. Nowadays I stab an enemy, and the ally next to it dies by the stab, things are a bit weird if you ask me.
