Because, back in VoG, when there were massive exploits and glitches, the best character to do them was the Warlock. After the Warlock, they wanted to have a titan or two for bubble defence and weapons of light to fight Atheon. Due to those factors early on, Hunters were often excluded from VoG due to being 'useless' in comparison, when in fact, they were extremely useful, and later proving to be far more superior in Crota's End, Prison of Elders and Crucible. With the patches to VoG as well, Warlocks were immediately cast aside as glitches were no longer available, meaning players no longer needed Warlocks to cheat. As such, the balance between characters became more apparent, with Titans always remaining as a stable, convenient character for strategy, allowing them to 'sit back and watch' the feud between Hunters and Warlocks. In the end, each class is good in their own way, but as far as anything goes, I view a hunter as always being more potent than a Warlock for many reasons. Hunters are faster, which is a fact, being the fastest class in game. A shotgun can easily shut down a Warlock self-res, but if comparing Supers to Supers, Bladedancer can easily shut down a Self-Res as well. Nova Bomb can shut down a Bladedancer, however, a Golden Gun can easily shut down a Nova Bomb in air and can be used from a distance, making a close range Hunter lethal even from far away. Within PvE as well, Hunters Supers don't prove to be as effective, however, their abilities make up for that. They can get in and out of tight situations easily due to their speed, as well as going invisible (without a Patience and Time) for sticky situations, such as reviving team mates. Between the 3, the Warlock can barely be used as a support class, whereas the Titan far exceeds in that ability and the Hunter capable of supporting a team as well. Warlocks have always been the solo guys, and as such, they often go hero mode in raids or prison of elders, thinking themselves to be above most players, only to get shut down and causing a hindrance on the rest of their team. Being a player with over 300 Raid activities completed and defeated every level PoE each week, including Skolas, I can easily confirm that to be a normal behavior among a majority of Warlocks.