ASW – Alternative hero leveling.

So, isn't Berserk supposed to be in Darkness? And Blindness? And why should epicness be achieved so easily? What value does it have then?

Very easily?

A demon in Light – that's interesting. But an elf in Chaos under a rainstorm – that's nothing special, just a standard thing.

The elf's upgrade was made for Chaos. Blue druids were also made for Chaos. That's the whole reason.
If you want to summon, you can get it in the guild – that's for low levels, and you'll have to search the map for high levels.
And why would an elf need it? Elf troops are swift and have high attack. There's no time to mess around with summoning.

Added 9 minutes later
By the way, I'd like to add Phantom to a separate perk, or give it with some weak unit (but not in summoning).