Why do you get a 3rd wave serpent?
I would also rather take wraithguard!
If you wanna stay with your list, I would drop 1 Wave serpent and upgrade the WL to a farseer. You are under the 2k points and still have points leftover to take a brightlance on each serpent (dont have the numbers in my head, you should check).
Else, maybe drop a nightspinner and get some dark reapers into the 3rd serpent. Or instead of the serpent if you wanna keep all the warlocks.
The good thing about the farseer is that he has a full smite and also ahs acess to different powers (Fortune, Guide).
Wraithguard do so much with the autohits. The enemy cant really charge you, and even if he does live the overwatch, they can fall back and shoot again and overwatch again with the autohits.
The weakness of your army is a gunline. Dark reapers could help here. Even more if you make the list ynnari if you include yvraine. Until the codex drops this would make your list rather competetive!
The nightspinners arent the most optimal choice but if this is what you have, try them out!