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

I think it's interesting to use cunning tactics. Yes, you can have fun with clever maneuvers, but a "rat tactic" isn't serious unless money is at stake. Is winning at any cost the point?
In short, it's clear that an online game is a huge field for creativity. Human thought and imagination know no bounds.
And regarding defense, yes, I agree – it's the most advantageous skill. The attack bonus is only 15%, while defense provides a 30% bonus, but the 2% chance of it appearing sometimes makes plans to upgrade it seem unrealistic.