At the start, skeletons are our main offensive force – ideally, it would be good to immediately convert all available experience points into simple skeletons (by killing, for example, peasants or goblins), and then proceed with upgrades and start dealing with more serious neutral creatures.
Without Necromancy boosters (the 10% "Necromancy" skill and the 5% "Undead" skill), we can only raise 8 skeletons from 55 peasants. And don't try to convince me that you'll have the opportunity to fight dozens of battles within a week with neutral creatures suitable for converting into skeletons – most often, you have to attack everyone (and raise everything, so that the experience points don't go to waste).
Besides, you can always raise a decent number of skeletons at the start + it's not easy to get undead creatures at the start + there are other perks... therefore, the importance of this perk tends towards 0! That is, it is useless, with some reservations!
Of course, "Magic Attraction" and "Unveiling Secrets," etc., also have many advantages, which are often more significant than the increased skeleton raising rate – however, this option is quite viable even without the "Amulet of the Necromancer."
Otherwise, it's useless compared to the rest of the upgrades. And you can't consider it in isolation – in that case, even "Morale" for a necromancer hero has "value."
So, I'm just more convinced of my own rightness. Even those "fantastic" 5 skeletons in the first week won't make a difference when we have hundreds of them.