First of all, I don't really understand why Elemental tries to simplify combat mechanics (one number for attack chance and damage). Is it to make the AI better understand the mechanics?

Generally, pen and paper games must simplify, because it's not fun to calculate hundred numbers for each sword swing. However, computers are good in number crunching, so computer games may benefit from more detailed models of gameplay mechanics - like combat.

Let's look at Dominions 3 combat system a bit - I don't know if many of you know it, but I wholeheartedly recommend it.

Weapons in this game have multiple statistics - damage, chance to hit (attack), defense bonus and reach. It's not so linear (biggest sword kills all), but presents interesting choice for the players. When there is a difference between weapon reaches (pike vs dagger, for example), the shorter weapon user must first successfully defend to shorten the distance. If he is unsuccessful, he suffers damage and is "repelled" back, and has to try again. This way, a formation of pikemen with lousy stats can hold at bay a pack of wolves - just because their long weapons offer them safety. Against a squad of mediocre, but armored swordsmen, they fall easily.

Another important point is that weapons affect defense. Obviously, a slender, renaissance sword with elaborate guard is better for parrying than a heavy, but unbalanced club. Should safety be preferred to ability to inflict damage? Here, units take different roles - one with better defense holds the enemy at bay, while other attacks at range, or attempts flanking.

Lastly, the difference between dodging or parrying the blow (defence), and absorbing the blow makes the system more varied and interesting. A heavy club may never hit an agile opponent, but if he tires down and his high defense stat plummets, first hit will will send him across the floor. A heavy armor may be impenetrable to normal blows, but a single hit with a magic wand may turn its user to stone.

Dominions 3 also has a great synergy of spells and conventional weapons. For example, Yomon has weak, but cheap archers that are nearly useless against armored troops, their arrows bouncing off harmlessly. A clever player will prioritize research of the "Fire weapons" spell, and because armor is only half as effective against flaming weapons , these weak archers suddenly become quite deadly. Undead player can cast "unnatural aging" global spell, and enjoy watching the enemy heroes wither and die of old age in a few turns, while being unaffected himself (long-lived Rylegh are another matter, though). Abysian troops from the underworld have infravision, so the global spell Eternal Darkness gives them considerable advantage.

And so on, the examples are numerous.

I am not saying Dominions 3 is better game, but some of its parts definitely work splendindly, especially the said combat system. There is a lot of detail hidden - the player may just read the result of a battle, watch it casually, or examine the log for detailed explanation of what happened ("oh, my giant got paralysed in the first round, and my footmen were decimated by arrows. Maybe next time, I will forge that protective ring and hire troops with shields").

An ambigious system where there is no clear "better or worse", but forces player to make interesting choices usually contributes to an interesting and immersive gameplay. Creating a competetive AI for such a game is usually quite impossible, though.