Balanced Units - A minimal balance mod for units

Don't the Druids and Mages bother you?

They already exist. That is, there are already 2 strong offensive spellcasters at level 4. Considering that level 4 is the favorite level for guarding passages to various zones (adjacent/defensive/treasure), it's already like a lottery – someone gets lucky, and someone gathers meat to keep losses at an acceptable level.
If you add another offensive spellcaster, and one with a 4th-level spell, and a mass spell at that, it will be a complete disaster.

Daughters of the Earth are the strongest or one of the strongest creatures at their level. Very strong ability (spell attack), high initiative, potential for retaliation.

A very debatable statement. The generally recognized leader is, of course, the Archmage. This is confirmed by numerous tests.

Considering that the upgrade was intended to be magical, it's very strange that the Daughters of the Sky cannot use magic from the first turn without Goblins.

WHAT? The Daughters of the Sky can't use magic? Are we playing different games?
Haste/Slow hasn't been canceled. 3 casts versus 2 for the Daughters of the Earth.
The Daughters of the Sky can only not use Chain Lightning. That's how it was intended – it's for use with the hero.
By the way, Goblins can be part of mixed neutral armies.
Also, there's the "Sword and Sorcery" week.

It's quite easy to defeat them as neutrals, as slowing and speeding up the weather won't help, and their combat potential is weak, which puts them in a losing position compared to the Daughters of the Earth.

The Daughters of the Earth are defeated as neutrals just as easily. They are simply a fast melee unit, nothing more.