Which magic schools should I choose for the late game? Or should I go for a specific artifact?

I'm not very good at standard maps or the TE mod; in fact, I'm terrible, and I don't even play them yet. But I play RTA often. Is Haven unbeatable? Apparently, you played against weak opponents or Orcs, because Haven is a rather difficult race, and they lose (according to the "rock, paper, scissors" principle) to Necropolis, and have equal chances against Barbarians. And about Wizards, that's not true; play for a longer time. Maybe some statistics and people will say that Wizards are weak, but in practice (in my own games, and in online streams), I see the opposite. In RTA, 60% depends on luck and spells (which is the same luck, what spells will come), and there is no obvious imbalance in favor of one race over the others.