First I will say, it's nice to see some variety but the list needs some editing to be Effective. You have quite a few model setups and upgrades that wont benefit you or your other troops. If those are the models you have then this list is really all you can strentch to do at 2000pts but i cant see it doing that well.
I will say what I would do with this list assuming you plan to buy a few extra models.
The Lord of change is perfect apart from pump him up to Mastery Lv 3. Flying and Divination is this models friend.
The Heralds need a drastic change. To me the Nurgle one is the only one that would do any good in their current form.
- Lesser Gift (AP2)
- Greater Locus of Fury (to get ur unit RAGE!!!)
DONE, cheap and effective enjoy killing enemy charatcers in one round.
- Exalted Locus of Beguilment (re-rolls to hit in cc and gets past that cock-blocking sergeant)
- Lesser Gift (AP2)
Slaanesh psychic powers I think are lacking so save your points for elsewhere.
- Mastery Lv 3 (take Change Primarius and two Divination powers [get the primarius for twin-linked 5d6 str 6 shots from this squad)
- Exalted Locus of Conjuration (for str 6 Horror shots on that Primarius)
A decent Herald. He shouldnt be in cc and wont benefit from gifts that much. Just put him in the Horror squad and watch even enemy flyers get mown down by sheer number of shots.
- Lesser gift (AP2)
- Psycher lv 1
- Greater Locus of Fecundity
you pretty much had this right. Take a plague power for decent witchfire/buffing ur plagubearers and take a cheap Etherblade for some sneaky AP2.
Ive moved your HQ's from costing 745pts to 680pts and made them much more effective with the rest of the Army in my opinion.
Drop the second Horror squad and bring your Bloodletters and Daemonettes to 15 or they will die before getting anywhere near combat . Plaguebearers to 15 for OCD's sake. Also add 1-5 Horrors at least to your remaining Horror squad to increase their warp charge points to 3. Tbh dont bother with the unit champions as you will have Heralds for that. You dont need icons that much unless your planning a big deepstrike attack. i would drop all the upgrades and keep em basic. Now you have 4 decent troop choices gone from 787pts to 600pts without upgrades and 20 horrors in one squad.
Right so now we are at 1280pts we can look at some hard hitting stuff.
Make you Soulgrinder Nurgle and give him Phlebm Bombardment instead of Warpgaze. Ur not gonna hit with that. Thats 180pts instead of 175pts.
Since you have Horrors to help with AA i will say he doesnt need a buddy, but your Bloodletters and Daemonettes would benefit amazingly from a couple of Skullcannons. These will add some much needed umff to your Shooting power and will cost 250pts for the pair, bringing your Hvy support to 425pts (total: 1705pts)
That leaves 295pts to spend on something Fast/Elite.
Flamers are fine, but make sure they target ONLY weak Infantry, elsewise until this gets FAQed ur just giving ur enemy FNP which will stack.
Thats 138pts leaving 157pts.
Ur current Fast attack choices are, at 2000pts, way too small squad size. For 157pts I have the perfect idea:
3x Plague Drones:
- Rot Proboscis
- Death Heads
These guys can shield you Nurgle Soulgrinder by hopping out of the way and then back in the way after shooting, and are tough and as fast as hell. They can tie up any units you dont want shooting in CC and can support your assault forces as they charge in.
Thats totals 1999pts of a varied and mixed list that yes requires some new vehicles and models but not many extra troops over all. Its still the same basic structure you gave (I think) so I hope this helped you out.