Questions about the gameplay of Heroes 6.

A strength-based hero without a "scary" passive ability like Retaliation is still effective. Retaliation is far from being the only thing that defines a strength build. ;)
As for which is better, I think the Warrior is superior, but overall, considering all factors, the game is quite well-balanced, and both are strong – the Mage and the Warrior. So, play whoever you want and "don't let these trivialities bother you," as Tevye the Dairyman would say.