Keep up the good work Bishop :).
I'll just add a number of points which I think could be added or expanded on:
Fire Dragons: Don't overlook the Firepike. It's quite handy when combined with Crack Shot against vehicles which have fired smoke or skimmers which have moved flat out. The extra melta range can also catch out the unwary.
Fire Dragons are not all that great against Terminators, especially Assault Terminators with Storm Shields, owing to the invulnerable save. It's far better for them to take on regular units, especially MEQs, vehicles, and/or monstrous creatures. Regular Terminators are okay as targets at a pinch, but not the primary choice in my view, unless you're fielding a very large squad of Dragons.
I think B is too low for their grade. They are the best unit in the elite section, if not the codex, so A would be my recommendation.
Howling Banshees & Striking Scorpions: I pretty much agree with everything you've said here.
Wraithguard: More useful as a troops choice than an elites choice in my opinion. I agree with your comments here too on the whole.
Harlequins: Kisses are essential, as is the Shadowseer. I don't think that they compare favourably with the other assault Aspects, owing to how much they cost, and their relative fragility at short range. Good players can get them to work well though.
Worth reminding players that they cannot take a Wave Serpent, and even if they choose to ride in one (which is a background issue), they cannot start the game inside it, meaning that it cannot move flat out on the turn on which they embark. Players tend to forget this rule.
Shining Spears: Good for hit and run attacks against small elite units and vehicles which haven't moved. Their main problem is that they are as good as dead if they get stuck in combat. I agree with your other comments.
Swooping Hawks: You're being a bit harsh with your grade here. They're very difficult to use, but they're alright against hordes, and they still have some ability to disrupt vehicles, especially squadrons and skimmers.
Not a unit that I would recommend for inexperienced players though, but I would boost them to a D or even C- if you're feeling ultra generous ;).
Warp Spiders: Don't write off Withdraw and Powerblades. If you add an Autarch to this squad it becomes rather handy for assault support.
For both Spiders and Hawks, deep striking can be useful, but whether you wish to discuss the advantages and disadvantages of this, I'll leave up to you.
Vypers: It's worth mentioning the EML here. It can be combined with the Shuriken Cannon to fire two weapons on the move (Plamsma missiles are defensive), and its range means that the Vypers can keep out of harm's way while firing from your board edge.
Dark Reapers: Not being able to move and fire really hurts this unit a lot. It's vulnerable to deep strike attack and outflanking assault units, and, as you say, cover really impedes its performance.
Unless, you're playing 2000 points, I think that they are too expensive to field, unless you want to gamble on a small squad of three led by an Exarch with the Tempest Launcher and Crack Shot for sniping MEQs.
The Tempest Launcher is good, but the unit is something of an Exarch delivery system, as it replies on this weapon too much in my experience.
The EML is okay if you want to fire krak missiles at vehicles, but this means the rest of the squad stands around doing nothing.
The Shuriken Cannon is cheap and probably the only option (apart from Surprise Assault) in the whole codex I would say is totally useless, because it does not have the range to work well with this unit.
Support Weapons: The artillery rules really don't do these any favours.
D Cannons are okay for area denial, and Shadow Weavers are okay against infantry, but the Nightspinner is far superior by comparison. Vibrocannons don't have a lot going for them in my opinion.
The main thing to add here is that if you attach a Warlock (s)he can fire the weapon, which is helpful, especially for the barrage of the D Cannon and Shadow Weaver.
These units are horribly vulnerable to deep strike attacks, and tank shocks so need to be well protected if you take them.
Wraithlord: Best taken in pairs of threes in my experience. They are much harder to destroy that way, and are more effective against vehicles in particular Otherwise, I agree with your comments.
War Walkers: I agree here.
Falcon: I agree again. You could perhaps mention the importance of taking Spirit Stones and Holofields though.
Fire Prism: I'm not its biggest fan, but it's rather nice at blowing holes in opposing armies which like to castle. Cover hurts it though, and they are more of threat when fielded in pairs.
Nightspinner: I recommend adding this, since its rules are official, and it's not a Forgeworld product.
Wave Serpent: Again, I agree, but you might want to mention the upgrades in more detail (see my comments regarding the Falcon).
I hope that helps.