My experience with our rivalry, even within our own fireteam, has been this (mind you, I'm a Hunter, so there's my perspective): Warlocks are crazy powerful. Honestly, it seems like they don't have really work for any of there kills. As Hunters, I think we kind of envy that. We work hard, aim carefully, and assassinate our targets. So we like to say that Warlocks, though really smart, lack skill. The reason no one has beef with Titans is that the Titan works well with either of the other classes. Side note: just from experience, I've seen Warlocks die much more often than Hunters.