I don't feel as if there is any bad clas for the raid. Warlocks can do some great enemy control with stormcaller while generating a good amount of orbs at the same time. Even my friends self revive saved us when we killed deathsingers at the last second but it still killed us. Hunters are great for their ability to make it so all hits are critical, making most yellow health bar enemies and some bosses a breeze. Titans are great for weapons of light or armor of light during bosses like oryx or golgoroth, or any boss in general. But yeah even though I main a warlock even I can agree that Titans and hunters are more usefull, but that doesn't make warlocks useless.