Pros of Nazir: He starts with Chaos magic and a powerful attack spell, which becomes even stronger as he levels up. If you're lucky, you can get the Mage skill on the second level and Secrets of Chaos on the fourth (another powerful spell, ideally Fire Wall). He clears the map quickly, and his troops include alt-upgrades for gargoyles and golems; one increases damage from Chaos magic, while the other heals with Chaos magic. Consequently, Nazir develops relatively quickly.
Cons: His skill progression is predictable for opponents (one magic is already known), and the longer the game lasts, the less useful his specialization becomes (by the third week, a mage should be using spells other than Fireball, such as summoning a phoenix, controlling creatures, or resurrecting).
Overall, Nazir is a decent average hero, but in my opinion, he is inferior to Hafiz and Nura as a starting hero, and to Ore and Razzak in a long game.