You've dumped 400pts into 2 characters; this is an awful idea. I'm not a fan of Eldrad, especially in a list where he basically has to join a DA squad, where his power is wasted inside a tank. At least drop Maugan Ra for more mans. I'd also thoroughly recommend dropping Eldrad for one of the basic HQs (Autarch/Farseer/Spiritseer). I think lists should default to the Farseer, although I prefer a couple of scoring Wraithguard units, so my personal preference obviously goes to the Spiritseer.
On your troop units- drop the exarch; he's just not worth it. Disarming Strike is pointless when you die in melee anyways, and PW+Shimmershield is just too expensive when you can achieve basically the same effect through cover. I also prefer Scatter Lasers over Bright Lances on Serpents, since it TLs the Shieldgun, but whatever floats your boat.
You also don't have enough scoring.
Warp Spiders are great, and you've set them up fine.
Dark Reapers are bad. You've basically spent 374pts on 10 Sisters of Battle that have missiles- that's a bad idea. If you expect them to act as AA, you're wrong- they can only kill one flyer per turn, and are stupidly easy to kill before your opponent brings their planes on. If you're really hurting for AA I'd just bring 2 Crimson Hunters for cheaper.
Fire Prisms are great.
"Knowledge is knowing tomato is a fruit. Wisdom is not putting it in fruit salad."
Also known as BaselessElm