Is Warlock good or useful in PvP/GTW?? Honestly I haven’t seen any WL 
but with the new evil spirit art, evil spirits can hit up to 5 targets, so invocation + evil sacrifice/mastema combo would constantly apply [Blind], I wonder if that is actually useful. Does it make sense to put Warlock with Sage? compression arts would group targets for Pole of Agony/Mastema, and Hole of Darkness also applies [Blind]. Can Warlock/Sage/Shadow be a thing? that build would give some control with Compression art and Shadow fetter, some survivability with Blink and Hallucination, damage and debuff with Condensation, PoA and Mastema, and chip damage and debuff with spirits. Help 
Unless you’re geared with endgame stuff, Warlock DPS will be too low. Spirit AI suxx, you’re not sure they will hit players instead of empty space. Of course you can do PvP with Warlock, it’s fun (usually I like my Warlock-FF for that), but don’t expect to do good.
I see! but Spirits now hit in AoE with the art, so even if it hits an empty space, it can still hit up to 5 targets around it, that’s why I thought that spirits could be useful as chip dmg and debuff.
And how do you use FF in PvP?
Levitation, move in the middle of all those swordies that can’t touch you and explode them with Blood Curse 
FF is less important in PvP now though because they’ve nerfed healing to oblivion, so the curse debuff is less useful.