Please, really would like any opinions and comments on this list.
HQ: Lord of Change (Warlord)
Lvl 3 Psyker, 2 Greater Rewards
HQ: Bloodthirster
2 Greater Rewards
These HQs look pretty strong, all told. Do consider swapping out a bad reward you get on the Bloodthirster (say, armor or the lance) for the Blade of Blood, which gives the bearer Rampage and is a second Specialist Weapon alongside the Axe of Khorne he comes with, meaning if he's fighting against more than one enemy model, he gets plus 2 to 4 attacks... while still being able to attack with his Axe.
Troop: 10 Plaguebearers w/ Plagueridden
Troop: 10 Pink Horrors w/ Iridescent Horror
Troop: 15 Bloodletters w/ Bloodreaper
Troop (2): 15 Daemonettes w/ Alluress
Hmm, dunno if this is quite the balance to be struck. Bloodletters are far and away worse than Daemonettes (who kill marines almost as well, and do far better against light infantry, terminator equivalent infantry, monstrous creatures and light vehicles, not to mention are cheaper by a point and have fleet and improved run distance), so I'd consider dropping the former for another squad of the latter. Similarly, I am quite underimpressed by Pink Horrors except as as a bubble wrap cushion for a Herald giving you Prescience (and perhaps Grimoire)--Plaguebearers are just that much more survivable, and you can DS Plaguebearers onto your Plague Drones without scatter if you opt to get the Drones a banner.
Elites: 3 Flamers of Tzeentch
Elites: 3 Flamers of Tzeentch
I'm not too sold on Flamers, especially multiple bunches of them. They're great for clearing out light infantry (especially Fire Warriors and Necron Warriors, thanks to their AP4), but ultimately they're just S4 flamers that are likely to buff the enemy squad. I'd rather take, I dunno, 6 Screamers, or a Skull Cannon of Khorne, or a unit of Seekers or Flesh Hounds.
Fast Attack: 3 Plague Drones of Nurgle w/ Plaguerider
Plague Drones look great on paper, though I've never actually run them (to my shame). Consider giving them a banner so they can precision drop in a squad of DSing plaguebearers, perhaps?
I realize that you are spending the 25 points on characters so you can greatly reduce the chance of your GDs getting Instabilitied by the Warp Storm Table, and that's a perfectly valid choice on your part. I'd probably be inclined to by a few more footslogging models, personally--but do as you wilt.