I guess it's just that you're bad as warlock, and needs to get better especially if u're coming from MoP overall gameplay.
Also, you didnt said if you're "6k GS" with any Resillence or not, otherwise is kinda normal you get almost shotted by any melee class if you're running with 0 resillence.
And, in terms of BG/World PvP, you should just watch some pvp videos...
https://www.youtube.com/watch?v=KUizH_eVcuA
https://www.youtube.com/watch?v=XXPFyAZZoNk
Just the first two i've find when using on Youtube: "Warlock 80 PvP"....