SC/BTS: Lots of people hold the opinion Chroma does. I disagree. I find nothing wrong with having the SC in the BTS formation. Generally, the BTS formation is tough so the SC has good protection. When/if it takes enough of a beating that it becomes vulnerable you can retreat it to protect both at the same time.

Guardians: If you have the models, I'd put at least 1-2 heavy weapons in every footslogger Host. Being able to place BMs is extremely useful. Even if you only have the 3 listed in your proposed list, I'd split them 1-2 across the foot Hosts.

Russ: I think your big advantage here is going to be activation count. You have 9 at 2000 points and he is burning 650 points on a single activation. That means you should be able to stall and swarm him after he runs out of actions. You can likely end a turn with a couple of unopposed activations and have a good chance to start the next turn with more activations, giving you a long run. So, if you wanted to play shoot-em-up...

Scorpions - move/pop-up/shoot
Prisms - move/pop-up/shoot

Next turn:
Scorpions - move/pop-up/shoot
Prisms - move/pop-up/shoot

That gives you 2 full rounds of fire, unopposed while the Russ have to sit there and take it, and your armor ends up back behind cover. Even if the Russ rally in between (and you may be able to find cover within 30cm to hinder their rallying), you'll have killed a couple units and they'll likely have 2+ BMs on top of that.

For an assault against the Russ, you'll also want to take advantage of that activation differential. If you start the next turn with a triple Farsight activation, you get a run of 5 actions without the IG being able to respond. If you were to do something like...

Scorpion - double to range of Russ, shoot
Fire Prisms - double to range of Russ, shoot

Next Turn:
Scorpion - shoot, stay in support range
Fire Prisms - shoot, stay in support range
Swooping Hawks - Engage Russ with Fire Prisms and Scorpion in FF support.

The Hawks would stand a decent chance to win. I picked those formations simply because they are the fastest and probably the easiest to position. You could even Teleport the Hawks in after you knew for sure you had the setup you needed.

However, the armor isn't all that great for FF support fire. If you managed to get one of the Guardian Hosts into range (like the mounted ones), it would work better because of their stronger FF. Also, if you manage to use some pop-ups to whittle down the Russ for a turn before this, you'll put a pretty big dent in the Russ and this will be much easier due to improved outnumbering, less FF coming back at the assaulting formation, etc..

Just a thought..

If you suspect that your IG opponent will run artillery (Manticores) you might want to give serious consideration to using your Nightwings. They are the only unit you listed as available that can interdict into the heart of the opponents army to strike at arillery. (Swooping Hawks can be too easily countered with a scout ZOC cordon).

An infantry heavy army will suffer badly under artillery fire for the whole game. And Eldar tanks are pretty vulnerable to non-LOS artillery too, since it nullifies the hit-and-hide tactic (and Elar armour isn't strong).

You might also want to consider the wraithgate, so all that infantry doesn't need to start on the table.

[Edit: Add to Nealhunt's tactics with positioning those units so that you gain a crossfire or two on the Russ for maximum effect. (Swooping Hawks are ideal for this so that the second turn's falcon/scorpion shooting is sustain fire with crossfire, very nasty.)]

personal favourite for infantry BTS's - guardians with wraithguard (and support weapons if you need to bump the points up by 50) or guardians with wraithguard AND wraithlords, especially if you're using a storm serpent so they can get into BtB. Keep it in the webway and you both keep it out of harms way, keep a nice 30cm exclusion zone around your wraithgate (woe betide any enemy that ignores that) and you get to choose what it attacks. The downside is that your storm serpent will become enemy target no. 1, but with some flak nearby and some rangers to screen it, it should stay alive long enough to deliver it's cargo (unless of course some git has a lunar cruiser and roles for tk3 before it even activates ).
Don't forget that a loaded up guardian fm and storm serpent has a maximum FF range of 105cm and is guaranteed to go into the fight without BMs. Add the 4+RA of the wraith constructs (though you can roll poorly like I did last game) to soak up hits up front and you should be able to wipe out pretty much anything you attack, even if it's in cover (negating your MW shots). 6 at 3+, 15 at 4+ plus support....

We ended up not being able to play as planned. Gives me a little more time to put a 2,000 point list together.

I think I'm just going to build my entire army around tons and tons of infantry. Hey, it's Epic. Why not.

Also: I really need to scratchbuild myself a wraithgate...

Yes, wraithgates are really good and should be used in an infantry heavy army. They are however quite easy to scratchbuild from plasticard. Good luck.