Let's take Elves vs. Undead as an example, focusing on the units. Dragons are weaker, and Nazgûl are basically cannon fodder compared to Draconians. Unicorns (with their magic resistance aura) will give Liches a run for their money, but only if the Unicorns reach them in one turn (which they likely will). Druids versus Vampires is the opposite; if the Vampires reach the Druids, they'll wipe them out, and they reach them on the second turn, plus they have an advantage in melee combat, allowing them to strike three more times with bolts without taking damage in return. Archers and Spirits are straightforward; I think it's clear how they perform. Dancers are also strong, with high attack power and area-of-effect damage; Zombies are unlikely to compete with them. Now, Dryads versus Skeletons – it's about numbers, although in equal numbers, Skeletons simply die silently. In conclusion, Elves should easily overpower Undead in terms of attack and defense, hit points, and resources, because the Elven Castle is significantly cheaper than the Necropolis Castle and also more effective in both attack and defense. However, this raises the question: "Why does Undead still put up such a good fight against them?" The answer is obvious: "A huge number of archers, even if they are only level 1." And you're saying it's just level 1! [U]

Added 5 minutes later
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Yeah, level 3 and 4 archers are great.

But I haven't calculated that yet; I didn't have time, but in Heroes 3, the damage output of archers was like this:
1. Titan
2, 3. Elven Archer, Lich (if it hits multiple targets, it moves to 2nd place in damage).
4. Cyclops
5. Human Archers
etc.
And regarding Heroes 5, after playing as Necromancer and Elf, it seems to me that Elves have higher damage output than Liches, even when the Lich uses mass paralysis.