"Necropolis" - changes to creatures of levels 6-7.

The slowest units should be the most powerful and tear through all other troops, all else being equal (except archers). Ideal zombies should be like that, but in Heroes, the "rights" of slow units to a decent gameplay are somehow restricted.

Ah, yes, slow zombies with dragon stats and fast dragons with zombie stats. Everything is correct. And the level of creatures doesn't matter at all in Heroes.
Right now, it's like that. At least, on an equal level. The only exception is Furies, but there the growth in a prolonged game is too small, so it evens out a little later.

Well, look, humans have Swordsmen and Knights. Orcs also have a similar unit that's good, but the zombies of the Necropolis are not well-designed. I completely agree with you on this.

All that's left is to hint that Swordsmen are the third level of Haven, while Zombies are only the second.