Like Windy said right now there are no other high tier troop in the other factions with that type of power. Which does make some sense seeing as knights were highly trained nobles meant to be able to survive. Better training and armor make a huge difference. Typically a knight was beaten by dehorsing them using long spears or even just huge numbers of soldiers to eliminate their mobility. And then they were defeated by sheer numbers, brute strength, or from carefully aimed pierces in the exposed joints. There is a reason knights ruled the European battlefield up until gunpowder was invented (and even then some armor smiths developed plate mail able to withstand early gunfire).
I feel as the rest of the factions are fleshed out you will see horseman be defeated more and more in areas where their mobility is limited so that they have to fight on foot. I have found that doing so makes them much easier targets when they are unable to just ride around and kill you.