A forewarning to those of you apes who are incapable of rational thinking, have the attention span of the arse end of a camel or have nothing useful to add to this world: this post requires you to follow my reasoning and see why I think cavalry isn't overpowered.
System vs. Behaviour
Firstly, I will define this model I will use to describe this perceived problem.
"System" can be defined as the mechanical aspects of CRPG relating to cavalry; such as cavalry weapons, anti-cavalry weaponry, horse statistics, etc.
"Behaviour" can be defined as the habits, tactics, methods of coping with or defeating cavalry players use against them, etc.
Secondly, there is an important practical distinction between something be overpowered because of the mechanics of the system and something being 'overpowered' due to the (bad) behaviour of people. I will paraphrase a conclusion relating to health and safety law that I think is a useful paradigm in this case. 'Systems don't make mistakes, people do'.
Thus, in order to make this argument, I will have to discuss why I think the System of cavalry in CRPG is innately balanced.
Countering Cavalry
I'll address plated chargers mainly: if the argument applies to them, it applies to other warhorses.
Players don't like the durability of the plated charger. Nor do they like its ability to take chunks out of a players health bar by riding into them. These are poor arguments against the plate charger because of reasons (mainly poor tactics) I will describe further below when I discuss Behaviour. But for now, I will make an observation. A great many players who complain about the plated charger attempt to defeat it using the wrong type of weapon. These same players may also fail to acknowledge that their builds have to have weaknesses. In the end of the day, if one player invests as a cavalry character, and you invest as a foot based character, you would be an idiot to not have acknowledged the threat against you from the cavalry. To that end, the polearms weapon set is a versatile weapon tree that includes many weapons that, if you had been built to counter cavalry properly, you would have no problem with.
The Only Proper Cavalry Counter (As In Reality) Is A Pike
Consider the Long Awlpike. It's a long weapon that can stop a horse attacking you at a 45 degree angle (a tactic used by cavalry players to give the infantry fighter minimum chance to hit). It can also be used with a shield; thus you have some protection against ranged attacks. It does 32 piercing damage and thus will penetrate the heavy armour of the plated charger effectively. No other melee weapon does such significant piercing damage at such distance. Consider also the Pike, its an extremely long weapon that is the ultimate cavalry stopper. It may not kill the cavalry outright, but no weapon should unless the cavalry player rides into it without guard up.
As for characters not built to be defensible against cavalry; it is a poor argument to be surpised when your two handed sword is not reliable weapon against a heavy horse galloping at you at full speed. Or when your bow doesn't little damage to the horse. Good armour would defeat arrows and histrically, a longbow was only effective against mail at about 20m. With a pike, or long awlpike, you would deter that cavalry and defeat it if it was stupid enough to repeatedly attack you. it is an equally poor argument to claim cavalry is overpowered when being attacked by multiple horseman. The fact of the matter is, it doesn't matter if your fighting cavalry or infantry: if you're being hit by multiple enemies you are at a disadvantage (and rightly so). As such, there is no Systematic problem, only a Behavioural one. Wrong weapon, wrong place, wrong expectations.
Other Misperceptions
Poor situation awareness is a common Behavioural reason why cavalry is perceived as overpowered. Consider this: for every cavalry player in CRPG there are usually more capable pike users. That means the cavalry cannot simply ride you over; a common perception by many is that a player on a plated charger (like TheFinn) rides over the enemy team because his horse is impregable. This is nonsense, more often than not the enemy horseman rides over a team because half of them are staring at a wall, leeching, mistime their pike attacks, do not have pikes ready, or expecting that their simple spear will stop the armoured horse. All it takes is one pike out of the entire team to stop a cavalry player. Note also, that a spear will stop an unarmoured horse. Poor situation awareness and team incompetance does not make cavalry overpowered.
Infantry also have mobility that a cavalryman doesn't have in that cavalry is terrain dependent. It is a poor observation to say cavalry is overpowered when standing in the open being flanked by horsemen. You will notice decent players stay near walls, jumping out the way of a charge, evading attacks at the last moment, and detering the cavalry with ready stab attack. Considering that a good archer can do massive damage by headshotting a charging horse, cavalry are actually very limited in what they can do if not armoured. The armoured horses themselves can be stopped a weapon like the awlpike.
Horse Archery
Mechanically, for a horse archer to be a more powerful shot they must invest in Power Draw and thus Strength. For a horse archer to invest in horse archery skills like riding and horse archery, they must invest in Agility. This mitigates the nightmare scenario of a plated charger mounted horse archer. Horse archers are also unable to use a shield when shooting. Once again, I believe there is nothing Systematically wrong with horse archers, but Behaviourally players are frustrated by horse archers but instead of commiting ranged attacks all at once towards the horseman or horse, they get seperated, singled out, shot and killed. No horse archer is impregable to arrows. They cannot wear heavy armour and they cannot equip a shield.
The Onyl Real Problem With Cavalry
In my opinion, the forcefield shield effect on cavalry is the only real overpowered matter on cavalry. The shield is too maneuverable and too effective on horseback with high shield skill. Fixing this is a matter of balance, but all the other situations describe above relate mainly to examples not involving a shield. Sometimes, a pikeman will end up hitting the shield instead of the horse despite aiming for the horse. In the wider dynamics of the game, this is not a major problem as multiple pikemen can and should be employed anyway, as described below.
The Real Problem Is Teamwork
The ultimate contributing factor to the effectiveness of cavalry is the way people play. Cavalry is effectively when ranks are broken, enemies are in disarray, and self-interest is greater than teamwork. Consider that most CRPG players do not use pikes effectively to protect their team or have an expectation that their messy barbarian horde team should be cavalry proof when it exactly those types of rag tag formations cavalry is made to destroy.
In practice, a good team will be able to deter cavalry from their team using pikes, good use of terrain, and having a stake in your teammates surivival rather than your individual kills. There is no decent cavalry player stupid enough to charge into a bristle of pikes. With the addition of friendly horse bumping in the latest patch; cavalry are further limited in who they can attack when looking for openings.
If teams got in the habit of using a mixture of pikes and other weapons when moving across open terrain and stay tight enough to protect each other but not so tight such that weapons start bouncing off people, then it makes it very difficult for cavalry to attack. If once the infantry enters combat and simply 'forgets' about the enemy cavalry: do not be suprised when you get a lance up your arse.