Well, it's not 'black legion' without any HQ's of mark of undivided...
It's a slaanesh oriented army.... period.
But... just looking at the army and not the 'name'...
HQ: DP- fine
Lord- good "assassination" setup, but really str 4 is not so great on the guy.
Elites: Chosen seem fine... they'd be better with an Icon of Chaos glory ( Black Legion right?)...
2 Dreads are very... dangerous with plasma cannons... but what-ever floats your boat, if you like to gamble that much, then they will be good for you.
Fast attack, min-sized melta squad bikers... are fine, but they NEED to be cover hopping to get the job done.
HVY: Split the obliterators into 1 squad of 2 and then 1 squad of 1., but since you have already used up all heavys... you could consider dropping an obliterator for the sake of even numbered squads..... but then again, you still need the extra Long range AT fire... /shrug
As for the defiler... I have the all or nothing mentality on vehicles... and I don't think you have enough.
The Vindi, IMO, should get daemonic possession always, not extra armor.
As for troops..... you want 10 man squads... and then special weapons, icons of glory, and some champs for powerfist and powerweapons...
My 2 Cents.
EDIT, RESPONDING TO THE BELOW POST,
Yes, I was hinting towards the crazed rolles... plasma can hurt your troops and other vehicles with a decent chance of killing infantry and glancing vehilces.