Hm, I did that and it didn't seem to work. But I just realized the Wizard in the campaign is different (pretty sure anyway) so maybe I did do it right... but campaign wizard ALWAYS starts with magic power+1, the wizard in the campaign never starts with anything else.
Are you talking about the campaign
tutorial - where the hero is chosen beforehand from a menu?
In the tutorial, starting skills are indeed fixed, and separate from the actual game mechanics.
Campaign and sandbox games rely on the same code to pick random starting skills.
If you attack an actual shard, and recruit a Wizard from the castle, he should always have Necromancy.
Try this binary if you can't get yours to work:
http://eador.online.fr/Eador_Vendayn_270.exe
Regards.