Necropolis or Castle (Which one is stronger?)

But what about the army? In that case, you can't move it. (Unless you have 1,000,000 gold, of course.)

We're talking about various tactics... Armies are passed along the chain if possible... Dismissing is clear – you don't take the troops with you, but sometimes just the presence of the hero in the right place at the right time can solve all the problems...

What do you mean? Can you elaborate?

If there are neutral units in the army that have a movement penalty on certain terrain, you can avoid it. If you place a neutral unit to the left of a unit for which the terrain is native, the hero will move without a penalty. For example, you can move mummies and nomads through a swamp without them incurring a penalty, as long as all the other units are swamp dwellers...
Place neutrals in the leftmost slot(s) when arranging troops, and there will be no movement point (MP) problems...

Another important point has been forgotten.
Humans (and others, except for necromancers) can be inspired! And they will make an additional move in battle. But necromancers only move once per round. This is a serious drawback.

But the opposite is also true... Necromancers will never have the misfortune that sometimes happens to humans... So, it's all equal here...