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I always choose Hafiz and consider him the best hero for the Academy faction because he starts with about 90 Gremlins, a Ballista, and a Wagon. After the Gremlin upgrade, they become significantly stronger, and the Destroyer Gremlins seem like a better option. Regarding Razaz, he's not a bad hero, but he's not as good as Hafiz. Hafiz can use a dirty trick against Razaz – three stacks of Destroyer Gremlins can disable the Golems.
It's better to develop Hafiz as follows:
1) Mechanics (3) – Ballista, Rapid-Fire Ballista, First Aid
2) Summoning (3) – Elementals – Fire Elementals – Earth Lord (if you have a Fire Trap)
3) Education (3) – (it's better not to take perks)
4) Light (3) – (it's better not to take perks)
5) Sorcery (3) – it's better not to take perks, but if the battle is against a mage, go for Counterspell.
+ Develop the faction skill "Wizard's Sign" – it's a MUST!
This way, you get a strong and dangerous hero.
+ and – Hafiz:
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Mechanics, easy start, fast development, strengthening of weak Gremlins
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His ability is weaker than other mages (Ora, Jallib, Nahriz), but this is only noticeable at levels 15+.