I'll tackle this, because it will be good to have a link to a list that describes itself as finished for the purposes of review, and because I'd like to show some respect to a newer player. You will be receiving a score from me using the 5/5 system as outlined in the Big List of Eldar Lists in the stickies on this board. Following is the critique I have given:
Background: 1
You've gone to great lengths to explain why you've chosen the units you ahve and how you intend to use them, as well as explaining your situation regarding your likely opponents. You hint a little bit at your background material, though it has not been included; if there are restrictions imposed on your list due to your background this would be good to share. All in all though, a very thorough job of presenting an army list.
Composition: .5
A good chunk of this list is allocated to non-scoring units, which could prove dangerous depending on how the rest of your army fares. Some of these units do not present too great a threat in themselves. You do have an excellent array of units though, with a lot of variety in the functions they will fill on the battlefield. You have only selected one combat-focused unit however, and at the 1850 level 2-3 would be much better, as enemy assaults are capable of shutting down your shooting. You've selected a good number of troops choices with an emphasis on volume of fire, and back this firepower up with some nice quality firepower in your heavy support and elite sections. You incorporate a good deal of mobility with a fair model count and a good quantity of units.
Utility: .5
Guide is an unnecessary power in this list; you will be causing yourself more trouble trying to take advantage of it than benefitting from it. Units that most benefit from Guide are ones that scatter or have a high quantity of BS3 gunfire [walkers, vyper squads, guardians, and support batteries/Tempest Launcher Reaper Exarchs]. Spirit Stones are unnecessary if you lose Guide.
Wave serpents are somewhat disposable if they need to be, but their cargo is not. Vectored Engines should almost be mandatory; they will prevent entanglement [somewhat] and heavy casualties due to crashes [moreso]. To not include them actually worsens the ability of this vehicle to do it's primary job [get the squad to its target in one piece]. The points spent on the farseer's guide+stones would be better spent here.
Banshees, Dragons, and Guardians are all quite nicely suited to their roles.
The Avengers are actually better suited to bladestorm as it is generally quite difficult for them to peel themselves out of combat once it is initiated. Defend will lessen the damage they receive in combat, but bladestorm does so as well by eliminating those who would make return attacks. The points are the same; you may wish to consider a swap, especially for situations where you need to eliminate an enemy who you will not be able to charge.
The reapers and Spiders are good; the spinneret rifle isn't quite as nasty to vehicles or swarms as the dual spinners and can inflict the same kind of casualties through "death by armor save," since every shot is likely to hit and wound. I like to see aspectless squads where it makes sense [the reapers in particular].
I would like to point out that falcons do benefit from some form of survivability upgrade [and I went for a year before buying Holofields]. This is because the squad and the tank itself are an expensive combination that need to be able to complete at least 1 "mission" [such as obliterating an enemy Talos near where you want your Howling Banshess to strike, as the banshees typically cannot wound a Talos due to their STR vs its Toughness, and because the Talos will quite happily destroy your Banshees]. That being said, if you've experienced bad luck with boxcars on those glancing hits, the simple spirit stones upgrade adds a lot to the falcon, and the Vectored Engines make it fairly unlikely that a single hit will harm the Falcon's cargo. One or the other would be helpful; in one turn you could easily be in striking distance of your target. I use Falcons as a two-squad transport, so that I don't mind buying holofields as I'm only buying 1 falcon rather than 2.
Flexibility: .5
The units you have selected, along with their upgrades, make for a generally strong list where flexibility is concerned. Doom helps your mid-strength weapons vs enemy units with high toughness, and you have a few decent AT rounds you can pump out, which can be supported in need by side/rear shots from your faster squads. You don't have too many repeat weaknesses, except that you do not make the best use of SMF for your skimmers, which could pose a problem for their continued existence as well as for their passengers. You lack a strong presence in the Assault phase, which will hurt your army vs an enemy who moves at great speed with assault-oriented units. In the event of a first-turn charge some of your critical support units may get rendered ineffective.
Ingenuity: .5
You discuss your plans for each unit and consider several different angles, but the critical weaknees of this army in the assualt phase is not addressed. This will be your biggest difficulty against a variety of opponents, especially those who play faster armies that are combat oriented. You sound unsure of some of your plans [such as giving Avengers some combat upgrades and yet questioning the notion of committing them to assault - better not to spend the points on an option you'll hesitate to use and invest them elsewhere]. Fundamentally this is the biggest problem you will face.
You should consider a firing order for your Reapers/Guardians/Falcon, as these three units pack firepower that is good against the same sort of targets. 21 shots that beat most armor merits careful consideration of its usage, so that you waste the least amount of shots possible. Probably Reapers/Falcon/Guardians is the best order, with the Falcon picking a secondary target should the reapers kill the primary one.
Your firedragons will be better working with your banshees, as the banshees can lock up enemy squads in combat and protect the dragons from return firepower a little bit.
Figuring stuff like this out ine advance saves time on the field of battle; having some good combos or a "playbook" to consult in the heat of battle can greatly improve decision-making under duress.
Total Score: 3, for a good army list.
Some kinks could still be worked out with upgrades and strategy; however, this list could be fielded and stand a decent chance of success. It may take stronger generalship to pull this list through in some situations. Others might be able to look at your write-up, field this list and expect a chance at victory.