"Newcomer-2011. Summer"

You should read the reports from when everyone used to play on SoD. When you read reports where both players have Necromancers in their folders, for any towns. Even 200-300 skeletons are never superfluous, neither in a Dragon Utopia nor in a Griffin Conservatory. It's simply profitable to level Necromancy because of the extra meat. It's not even just profitable, it's practically necessary.

For a normal player, this is not a problem.

For a normal player, winning against a Necromancer is not a problem.
I'm not disputing that Necromancers are strong, but not always. First of all, it's always a loss of tempo. Secondly, the anti-morale, which can be a real pain early on, and not just then. Thirdly, it's a fairly useless skill for the entire first week.
If you look at the random map the topic started with, Inferno is a pathetic imitation of a mother with the current restrictions. Isleen on a swamp... Well, there's nothing to talk about there either. The same Logistics heroes, under normal circumstances, outrun them so much that the little skeletons will be nervously smoking on the sidelines.
Therefore, imho, reducing the percentages or a new calculation system would make them quite balanced. That is, not blindly choosing them for folders, but based on the situation — whether there are creatures to raise from, the availability of Necromancy artifacts, and so on..
As an alternative, just weakening the skeletons themselves.