Why isn't the rogue sapping?
Sounds like a bad pug.
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For the OP:
Warlocks, despite what a lot of people say, aren't easy. The ".fear/laugh" method doesn't stand up to any decent opposing player (pvp), and against mobs you'll attract too many [mobs] to easily handle (pve). A lock comes down to preparation and instant decisions, so it really forces you to concentrate.
For pvp, a good player with decent gear can beat any class, with rogues being the partial exception (anti-class). While it's possible in a 1v1 setting, it's probably the most difficult (imo).
For pve, we can solo almost anything (like a hunter).
For raids, we have a well defined roll as a main dps/cc class, with good survivability (drain health) and raid bonuses (imp bp, rit. of souls, soulstone).