I'm personally annoyed about how spears work in VC, especially if you consider that the other types of weapons are just the one handed making just two choices of weapons. Many times I've found myself facing an opponent, using a board&spear technique, only to have all my attacks parried by simply holding a button by both Bots and Players. Also, in VC it's more important where you strike with your weapon than in Warband and spears are mostly aimed to hit the belly, which is also the most armored part so usually an attack tends to end with a bounce (and the inevitable sword right to my head, which can make it explode), so having the possibility to do an overhead attack to hit the helmet can help a lot, especially in Viking Invasion mode where it's easy to be overwhelmed by bots.
But, guys, there are different types of spears. What about leaving the long spears just like they are right now and making the short ones capable to do an overhead attack with shield? After all, I can imagine that a long spear wielded with one hand require more strength, if not for the weight, at least for the length, while the short ones can compensate the lack of reach with more maneuverability, making them worth to be taken. Also, this will make them available in a shield-wall because with the two handed overhead attack they hit nothing because most of the length of the spear is occupied by the hands.
Speaking of the animation, I've noticed that in SP, when I command my men to form the shield-wall, my animation of attacking with the spear change, with the trusting attack of sword, so I attack with my spear over my shield. Perhaps this can be a base for a new overhead animation? Or maybe it is a bug, I dunno.