I disagree about Orlando, specifically in the context of WGE and faster gameplay. Casters are always dangerous as casters; the moment when their spells cease to be effective simply doesn't arrive. :)
Considering the significantly cheaper spells, stealing even a few units of mana can deprive casters of the ability to cast key spells, or any spells at all. Therefore, the specialization should work even at low levels.
For example, spells of the 1st circle cost 1-2 mana, and some casters have a mana pool of 5.
I'll add, so you don't think that all magic is cheap:
1) 1-2 mana
2) 3-5
3) 6-8
4) 10-15
5) 20-30
For each unit of knowledge, a hero has a maximum of 5 mana, not 10.