(I'll leave this here for you to mull over again deamonwithin

)
I generally prefer FateFiend, I feel you get more bang for your buck.
Something along the lines of:
1. Fateweaver - 333pts.
2. Herald of Tzeentch - 110pts.
w/ Chariot, We are Legion, Master of Sorcery, Bolt of Tzeentch.
3. Herald of Tzeentch - 110pts.
w/ Chariot, We are Legion, Master of Sorcery, Bolt of Tzeentch.
4. 6 Fiends - 190pts.
w/ Unholy Might
5. 6 Fiends - 190pts.
w/ Unholy Might
6. 6 Fiends - 190pts.
w/ Unholy Might
7. 5 Plaguebearers - 100pts.
w/ Chaos icon
8. 5 Plague Bearers - 100pts.
w/ Chaos Icon
9. 5 Plague Bearers - 100pts.
w/ Chaos Icon
10. 10 Horrors - 210pts.
w/ Bolt of Tzeentch, Chaos Icon, Changeling
11. 10 Horrors - 205pts.
w/ Bolt of Tzeentch, Chaos Icon
12. Daemon Prince - 220pts.
w/ Flight, Might, Mark of Nurgle, Noxious Touch, Daemonic Gaze
13. Daemon Prince - 220pts.
w/ Flight, Might, Mark of Nurgle, Noxious Touch, Daemonic Gaze
14. Daemon Prince - 220pts.
w/ Flight, Might, Mark of Nurgle, Noxious Touch, Daemonic Gaze
Total = 2498pts.
I've used this a couple of times and it's performed quite well. One thing you must be careful of is charging the fiends outside of FateWeaver's bubble. Also, Just make sure that everything but the Plaguebearers (and possibly the horrors) are within Fateweaver's bubble to make sure you get those re-rolls. You could also drop the Icons if you want for some other goodies like Iron Hide on those princes? Up to you,
Good luck,
Iranna.