I'd even call him the most powerful domination-magic wielder in all Aventuria, regardless of magic tradition…

But now that it is mentioned: why aren't there more domination- and influence-spells in the game? Some wouldn't be to hard to integrate, surely.

There are some though. Horriphobus, Plumbumbarum, Master of Animals, Meek you be, Sleep of a thousand sheep… and with the introduction of the Geode, there will probably be even more in River of Time.