That's because the warlock isn't meant to have built armor. What do you want a third grenade? Other things a warlock is meant to be a support class so all there gear is armored to that. Support. Where a titan yeah all that's awesome but your titan should also be in the middle of a group of enemy's where he needs those buffs same and with a hunter should be a little ranged but do heavy damage. It's all pretty balanced I've not seen a single problem front the different armors. I don't ever even look to see what my armor gives me. The only one I ever did was the exotic helmet for my hunter to get a 4th shot for my golden gun other then that my warlock does just fine with his armor. My helmet helps with revives just like I built it for a sprinter but does damage when I need and buffs my friends abilities