My two cents,
Don't bother with the assault squads and pack more bikes instead.
Beef up your regular bike squads by attaching attack bikes to them (bringing their number to 6 per squad, and increasing their wounds by 2).
I'd also go with a static unit that can fire directly, since your bikes will probably be turbo-boosting in your first turn. I'd recommend a predator destructor w/ lascannon sponsons over that whirlwind.
Lastly, I'd go with a chaplain, instead of a captain...might be a little pricier, but hey, you're going into assault right?
And yeah, White Scars still work...you just need to pack tons of bikes (coz' if you're using landspeeders aplenty, you'd be playing Ravenwing, yes?
).
Here's more or less what I had in mind for 1,000 pts:
HQ-Reclusiarch w/ bolt pistol & crozius, bike, frags, melta bombs - 122 pts
Elite
-2x
SM bikes, 2x
SM bikes w/ flamers,
SM bike vet. sgt. w/ power weapon, bolt pistol, and melta bomb, attack bike w/ heavy bolter; all with furious charge - 270 pts
Troops
-2x
SM bikes, 2x
SM bikes w/ meltaguns,
SM bike vet. sgt. w/ power fist, bolt pistol, attack bike w/ heavy bolter - 260 pts
-2x
SM bikes, 2x
SM bikes w/ meltaguns,
SM bike vet. sgt. w/ power fist, bolt pistol, attack bike w/ heavy bolter - 260 pts
Fast Attack
-Landspeeder Tornado (heavy bolter & assault cannon)
Total points: 992
Model count: 20
If you want a static shooty unit, like a predator destructor w/ lascannon sponsons, you could remove the Tornado, the chaplain's melta bomb, and one biker from one of the troops choices. (sorry, I just don't like whirlwinds...I mean, if its indirect fire, and it isn't a battle cannon, earthshaker or a D-cannon, then I don't think I'd bother...but that's me)
Hope this helps,
Farseer Iakobos
Craftworld Iyanden