Same advice as Ryu really. Exalted Flamers are naff because they don't get relentless, so they cant really move and shoot. What makes them even more stupid is that Flamers are Jump Infantry, while the Exalted version is just Infantry. So by including them you actually cripple the unit.
Splitting up the Screamers is a good idea unless you plan to deathstar.
Other than that, looks promising.
Other sneaky thing you can do is stuff like buying yourself a Bastion for 75pts if you want upgrade with a quad of Icarus and maybe an ammo store for rerolling shooting hits of 1s. Put the 4 heavy bolters facing towards the enemy and enjoy an additional 4 X 3 BS3 S5 AP4 shots that DON'T have to shoot the same target as you fired all the pink horror fireballs at
(though this works better with Blood Letters as they are BS5).
OR go for something like a Firestorm Redoubt to act as a bunker with 2 self firing Quad Icarus, or Punisher Gatlings or Battle Cannons. Shooting your Magic Fireballs from inside your AV14 Building shell.
OR a pair of Vengeance Weapon Battery with Punisher Gatling, Battle Cannon or Quad Icarus again. If you allow something like Blood Letters to fire them you have BS5, if you go for Herald of Khorne you have BS7. Having -5 or -7 (or if you went for Skulltaker it is -9) to the scatter dice is pretty awesome with Battle Cannons
. Lord of Change also makes good crew if you plan to keep them near the back with BS6 and as a Monsterous Creature he can fire 2 weapons, so can actually take control of 2 Vengeance Weapon Battery at the same time. Oh and if you arm him with Greater Reward for a Mutating Warpblade. This means when you slay an enemy character or monstrous creature (doesn't matter if you use the weapon to do it, or a magic attack or whatever, as long as the bearer does it) you can roll a 2+ to turn it in to a spawn. This is insane when using Gatlings or Battle Cannons, as you could kill multiple unit Sergeants and Characters with 2X 20 S5 AP- or 2 XS8 AP3 Large Blast shots respectively.
Also the nice thing is that it isn't to hard to convert up 2 things to be big mutated things that spit out warp blasts.
The other thing I noticed is that you have 3 HQ choices as you have Fatey, LoC and the Heralds. This means your army is currently Unbound as you cant use an allied detachment with your own army.