This is gonna be an endless moot point if some things aren't clarified. Firstly, we (or, more precisely, the EB team) should decide what we expect from particular unit(s) on the battlefield, given the limitations of MTW2 engine.
Then, however, it must be decided what we want from the game in terms of overall balance in the singleplayer mode, which accounts for the greatest part of average player's gaming experience. And singleplayer mode means facing AI opponents. In such case, those are bad opponents, even if better than RTW ones.
If we introduce impenetrable heavy infantry from the front (I'm not saying that it should be the case, as it's just an example), human player would be smart enough not to use his/her cavalry in a suicidal manner. AI, however, cannot be taught this. Handling the cavalry would be one of the trickiest things to do on the battlefield, as they could only be used to flanking manuevers, something which on MTW2 engine will always be much easier to perform for a player than for the AI. Therefore, if we want some challenge from sp game, we must make a compromise of sorts and such compromises are present in EB1 (some are better than others).
A good example would be the balance of primary and secondary weapons of "lancers" in EB1. They are full of compromises. Their primary weapon is perfect for charging, but it should be really effective only when charging from the flank or rear and it shouldn't be that great in prolonged melee. However, in EB1 AI can't switch to secondary weapon, so the lancers must be able to fight with their primary weapons with at least average efficiency, as they do in EB1. Also, the lancers should retain their ability to cripple enemy with flanking charges, as they do in EB1. Switching to secondary weapons should also be possible and at least useful in some situations, e.g. when fighting lightly armed opponents with swords (so that players can utilise this) and that's the case in EB.
This impressive balance is achieved by utilising weapon delay attribute (so lancers are not overpowered in melee), low attack value (see above), very high charge (so the lancers are much more powerful when charging) and lethality values (so they are not underpowered in charges from the flank or rear and in melee in general, for the AI's sake) and armour-piercing attribue (so units with high armour value are not immune to flanking attacks). Secondary weapon, in case of swords, have much higher attack value, no weapon delay and lower lethality, so they are perfect when fighting opponents with high defence and low armour rating. Of course, the balance is not perfect, even because of existance of experience stat (which can throw the balance of in many parts of EB1 combat system). Also, as pointed out, sometimes lancers are too good versus armoured opponents in melee and it's not practical to change to secondary weapons. Personally, I would give "area" stat to swords and decrease number of soldiers in an unit to remedy this problem, but that's another topic.
Long story short - there are many things to consider when balancing the statistics and things that look realistic on paper aren't always the best ones in practice.
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