I would put Tyrax in third place. He has good attack power, speed, and durability, plus excellent skills. Starting with Tier 1 units makes building an army easy. Any other faction would be second. Once you take the swamp, you can add health-boosting bears and ogres. With wolves, the offense and tactics become incredibly powerful.
This probably refers to the "The Shadow of Death" expansion, right? I highly doubt that most of this applies to "Heroes of Might and Magic III: The Succession Wars".