ASW – Alternative hero leveling.

Don't forget that summoning depends on magic. Chaos also depends on it, but the sheer number of units compensates.
By the way, only the Hive and Wasps have a natural summoning ability, and they also deal damage.

But don't Sylvan units grant magic? Besides, Wasps don't really need magic.

Besides Wasps and the Hive, Elementals, Phoenix, and Earthquake also have natural summoning abilities. And I don't understand why you're now rejecting the idea that Elves need summoning for aesthetic reasons?