Top level pvp player agrees that warlocks are subpar in pvp
The discussion starts at 2:00 into the video. Essentially warlocks fall short in high level pvp in 3 ways:
1) mobility, 2) melee, 3) class ability. The solutions are simple, more "speed". A faster jump, a faster melee, and faster class ability animation are needed for warlocks to be on par with the other two classes.