My only dislike about them is current pact CD and strength + LOH healthstone.
Combined with soul link and and soul leech I feel like I’m hitting a brickwall with a 45 second pact. 
If pact was like 1.5 or 2 minutes it would feel a bit more manageable and if healthstone didn’t heal THAT much.
Then there is demo 
the amount of things I have to do to take out a demo warlock ha. Inexperienced ones.
Actual good ones no chance