Dropping the reaper/warp spider squad sizes were something I'd considered, but there's such a huge amount of points on the spiders that's sunk into the one exarch to keep them functional (withdraw) that the other spiders are relatively cheap. Dropping a reaper or two might make sense. I can't pull anyone from the wraithguard - they have to be 10+spiritseer to count as scoring. If I were to downsize them at all, I'd just drop to 5-6, take them as elite, and call it a day with points to spare. Swapping the reaper exarch over to a EML I don't think makes sense; if I'm going to shoot at tanks, I'd be better off just dropping the squad and grabbing a third WL - that way, the weapon platform is more mobile, and more intimidating to charge.
Swapping the reapers for a pair of scatter laser warwalkers is an option though... S6 is enough to pop open rhinos, especially early game. It'd save me 97 points. If I pull the exarch from the DA squad, that's another 32. The spiritseer with the WG only has embolden because I had no other use for those 5 points, so that's an easy target. There were 4 points unspent (total was 1996 before). That's all but 12 points... so I can drop one DA and that should add up to 1850. I'd lose out on the long range anti-marine firepower, but I'd gain some long-range bulk shooting (enough to compensate the loss in the DA's. I keep the core block of stuff going up the middle though, and my long-range weaponry becomes entirely move-and-shoot, which is nice. That may be what I end up doing.
Modified list:
HQ:
(210) Eldrad
(155) Avatar
Elite:
(192) 10 Howling Banshees: Exarch w/ Executioner, Acrobatic, War Shout
Troops:
(381) 10 Wraithguard: Warlock w/ Spiritseer upgrade
(100) 10 Guardians w/ Eldar Missile Launcher
(100) 10 Guardians w/ Eldar Missile Launcher
(108) 9 Dire Avengers
FA:
(174) 6 Warp Spiders: Exarch w/ Dual Deathspinners, Powerblades, Withdraw
HS:
(120) 2 War Walkers: 4x Scatter Lasers
(155) Wraithlord: 2x Flamers, Eldar Missile Launcher, Bright Lance
(155) Wraithlord: 2x Flamers, Eldar Missile Launcher, Bright Lance