How to play against Wizards?

Chaos - a ring, a block, spikes.

but when distributing damage (magic, army) - it can also be defeated.

Even a two-week newbie will outplay you with such a build. And some people are still trying to teach great necromancers.

Outcasts are actually small.

Outcasts are actually medium.

Well, I don't know, isn't Earth a large map with a lot of neutrals?

There are a lot of neutrals.

which means there won't be mini-arts against magic.

Read the documentation and don't embarrass yourself. A large part of the mages' army is protected from chaos, one way or another.