To my understanding, along with some others posted above: Shields do not offer any defensive stats such as armor like they do in several other games (i.e. EQ and WoW). Shields offer a different set of skills that provide more control such as Shield Bash. The warrior's Shield Block only lasts for 3sec and it is on a 30sec CD, which is phenomenal if you're being focused and can't dodge out of the way, but it is still a situational skill.