Which units would you replace in the Dark Elf faction?

there is indeed an "Achilles' heel" - demons with their imps/devils

Yes, it's unpleasant to play as Dark Elves against a Demon, but the DUNGEON army is so unique, strong, simultaneously stable, and full of various tactical options that it can defeat anyone even without mana. When playing against a Warlock, you never know which unit to expect a trick from; any of them can surprise the enemy.
I believe Dark Elves are a race with the widest range of moves and all sorts of strategies at different levels; they are like a snake, capable of wriggling out of any situation. Much of this depends on a successful selection of units, so it's better not to change them.
It's difficult to play Dark Elves well, but what potential they have...