Come on, don't brag:) (just kidding)
Of course, it won't take 3-4 weeks for Necromancy to reach level 5.

The point is different. It's easy for any hero to gain 5-8 levels (initially), which means either magic of the 4th circle or a combat branch (defense + ranged attack, for example), and so on. In other words, the hero becomes not so much combat-ready as useful for performing specific tasks. But what's the use of a Necromancer at level 5-6 in battle?

Regarding this map. Besides, a strong Thief will quickly come to the Necromancer's aid, and no Necromancy will save him).