Yeah, in case you have never noticed, most warlocks use self Rez in PvP/PvE. In PvE it's [b]can be[/b] good in nightfalls and raids. But most of the time it is useless and does not generate orbs. Same goes for PvP. Die, Rez, Repeat. Now if you're going to use it whenever it's different. Because titans have striker to clear out huge amounts of enemies and bubbles to hide in. Hunters are the best against high priority targets in raids or nightfalls (Using gunslinger). And nova bomb can be useful and team supportive but not as much as the other classes. Even bladedancer can go invisible and revive. I say lack of team support because compared to the two other classes, they have less uses for their teammates. This does not mean they aren't team supportive, because a minority of titans and hunters are not team supportive builds just like there's a minority of warlocks that have a team supportive build. Tl;dr The other two classes are usually more supportive then warlock.

Titans: fist of panic for large enemies/ generates many of orbs. Bubble, weapons/blessing of light. Not to mention its great for when your about to die. Warlock: self rez for those very intense moments. They have that ability which gives nearby teammates a cool down. Nova bomb for those large crouds and generating a lot of orbs. Hunter: able to go invisible and revive (very useful at times) golden gun for orbs. (great with achlyophage) ark blade is good for clearing out large amounts of mobs such as thrall. So all classes are all useful in many ways for different situations dont shame on different classes because together we are a perfect team.