Your favorite hero...

Haven is a rather unfortunate choice in a standard game. I would say it's extremely unfortunate. As always, everything boils down to the stupidity and difficulty of implementing the racial ability of the Elves. But in a duel, yes, it's overpowered there. P.S. I assure you, even if you only level up a Warlock's Knowledge in the corresponding buildings, his power will still be very, very impressive. Although, perhaps, by Sorcery, Antoxic meant: "If a Wizard doesn't take magic schools, especially the Chaos school, then the damage inflicted by his spells will not be significant enough to stand out from the relatively low damage of a Knight or an Inferno." Well, I can only say one thing about that: if a Necromancer doesn't use Necromancy, dark spells, raising the undead, and undead in general, then he won't be that strong either.