Are we talking about multiplayer here? Even with a shorter spear than the cavalryman's lance, you can sometimes stab them first. I certainly find the war spear, when wielded 2 handed, is a good match for any lance apart from the great lance, and even then the slow thrust of the Great Lance makes avoiding it a good possibility. Yes, thrusting from horseback is very useful, but getting the timing right is what decides who gets hit. I consider myself a pretty decent horseman and footsoldier, I like to fight as cavalry against infantry and vice versa. I have my successes but also get killed, as both cavalry and as spear foot. It is far from a forgone conclusion that a spearman will be beaten by a lancer, even with a considerably longer lance. Obviously a lancer can be ultra careful and keep his distance, but then it is easier for the spearman to block or evade. The speed with which the distance closes can count against both the cavalryman and the footman. I don't see many horsemen approaching spearmen freely, they only do it cautiously, when the spearman is distracted (or cav ends up dead).
Still, a slight (very slight) reduction in the arc of thrusting might be ok in my opinion.
