It seems to me that Berserk and Hypnotise don't depend on Spells Power like H3's Hypnotise (correct me if I'm wrong).
If it is this way then they may be too powerful. Consider a level 5 hero with Expert Dark Magic can cast Berserk and Hypnotise with massive damage (if enemy's army is big). This is too powerful I think.
I think Berserk and Hypnotise should depend on spell power: the greater it is, the bigger the stack you can affect (X experience points of creatures for each spell power).