What kind of magic do you like the most?

In online games, such long durations are not typical. Unless it's by agreement...

Which happens quite often, but the forum is full of threads like "help me defeat a gnome on a very large map" and so on.
And in the early stages, summoning doesn't really help much – either magic is underdeveloped, or the hero's level is too low, with all the consequences.
Perhaps, if you focus on developing only one summoning skill, but then there are other nuances...
But the fact remains: the longer the game and the larger the armies, the less effective summoning becomes, and the same goes for Chaos.

So, the only drawback is number 2.

If so, then number 3 is also a drawback.

It's not very effective against Wizards. Titans, stools, golems – no mind control spells. Genies have resistance. The hero has a magic mirror.

Stools and golems are not the main strength of wizards; genies die quickly. Vampirism on your own units, blindness on titans, control/berserk on rakshasas, and then hit the rest with weaken, slow, vulnerability, and debuff – and you're golden! :smile03:
The magic mirror is certainly a problem, but firstly, if it reflects a spell, it will reflect it on your own units in half the cases, unless you're Jalib, of course; and secondly, it won't reflect area-of-effect spells.

It's not very effective against elves. Elves often develop Light magic and counter it, plus unicorns with aura, plus they can take "magic resistance," and luck is almost always taken.

Magic resistance is random; you can't rely on it too much. Of course, they can counter area-of-effect spells, but almost always, the necromancer will cast spells more often, and even if control/berserk is cast, it can decide the outcome of the battle.

So, the downsides are much simpler here.

Well, two half-downsides against two)))

Don't get too carried away with schools of magic. Of course, Chaos is useful for a Warlock in the early stages, but spending two skill slots on magic can be dangerous. I would develop a secondary hero with Chaos magic...

In my opinion, two schools of magic are just right for mage heroes, and I wouldn't risk developing only one summoning skill for a Warlock.

Added 9 minutes ago

They've already figured it out: MAGIC_SCHOOL_SPECIAL, it exists in the xdb files of some spells. Any player can use almost all spells from this school. It has no tactical drawbacks, unlike other schools.

They've figured it out, but how do you develop it? I don't see any skills or abilities for neutral magic. Darkness, light, chaos, and summoning have a clearly defined form, while neutral magic can simultaneously include a lot and very little; it's something amorphous, so it's not quite appropriate to compare it.


Added 10 minutes ago

No, you can take two schools of magic, but it will inevitably be to the detriment of something, while with one school, you can live without any particular problems.

If you take two schools of magic, you can develop a Warlock like this: 2 schools of magic, education, spell power – definitely, then you can take attack or logistics, depending on the circumstances.
Everything you take and don't take will be to the detriment of something) even logistics is completely unnecessary for combat.