Battlefield size in Heroes 5.

Wow, they really went all out! There might not even be seven different dragons on the map!

That's not quite right.
Dungeon has a 6th-level unit that occupies only 1 square. The situation is different for all other factions. Humans still have priests at level 5, but the smaller monsters of other factions are limited to level 4. Need I say how huge an advantage Dungeon has, especially considering that matrons are casters?
The developers are wrong. They are completely wrong.