Uh, if you see a lancer soon enough to try to dodge, why don't you just block down?
LOL, I do, all the time, but thats like saying if a 2hander is swinging at you, hold up a shield, doesn't make a class somehow not OP just by blocking them (and by the way other than crushthrough weapons, lancers have the only UNBLOCKABLE attack - couched lance). In actual combat, just go watch NA 100 server with 30-40% of the server going cavalry. You can downblock the first cav, he tramples you, seccond cav following easily lances you. Or the more common scenario, you downblock or use a pike all the way to an actual melee fight and as soon as you engage anyone they can turn their horse on a dime (arabian) or charge halfwaya cross the field in a few seconds (courser) and either couch you or lollance you while you are meleeing.
Most cavalry kills are not people being unaware but cavalry having much higher speed and maneuverability and a much longer weapon than most allowing them to take advantage and easily kill anyone engaged in melee. When you are on a horse just skirt the edges of the fight see someone actually try to melee anyone and you can get there within 2 seconds and lance them in the back, its incredibly easy way to rack up 20, sometimes 30 kills on a map with minimal risk. The supposed counter of get a pike also doesn't work in that scenario as you cant melee very well if you are using a pike or if you are meleeing or trying to attack a different cavalry person, the same thing happens to you.
The main reason this is possible is because of the huge bonus the riding skill gives to speed and maneuverability, which wasn't horirble as long as there were few cav on the battlefield (just like when there were few throwers on field before january), but as people have acquired more gold, upkeep is more manageable for many using a horse and the imbalance becomes readily noticeable as they proliferate. It was actually much easier to dodge a lance before January even though horses lost 2 speed because the riding skill requirement of 6 agility kept riding skill lower, but now with the average riding skill being half again as high as it used to be it actually made horses faster and more maneuverable with 2 less speed stats. Most lances outrange all but the longest polearms (think pikeman but with much greater mobility and a much larger speed bonus), so unless they are really average or bad they will hit you before you strike their horse and downblocking doesn't make them go away they just spin a 180 and hit you when you are meleeing or facing a different horseman.
The best evidence is just watch most fights nowadays and the practical reality of any map with even remotely flat terrain, inevitably cav completely dominate the battlefield every round. Don't look at your own self as a horseman but how it actually plays out ina balancing or unbalancing role in large group fights with multiple cavalry. Inevitably, individual cav don't think speed/maneuvarbility need to be reduced, but thats never the whole picture from agame balancing perspective.