[darkreever]

Librarian, Null Zone, Avenger

Good choice, cheap and effective

Tactical Squad, Flamer, PF, Las Cannon - Rhino

I'd suggest a meltagun for this squad, tends to compliment the powerfist; otherwise a power weapon and meltabombs compliment the flamer pretty well.

Scouts w/Snipers, ML

Would recommend camo-cloaks for this squad, not that much more and its always nice having cover saves equal to scout or tactical marine armour.

Devastators, Las Cannon, Plasma Cannon, Razorback TL Las

A little unfocused, I would suggest doubling up on one or the other and then you would be fine. (I think plasma is cheaper, but more risky overall and less effective against heavy armour.)

Land Speeder x 2, MM, HF

Good choices, as has been said before make sure to split these two up.

Predator w/Las Sponsons

Good choice

Dreadought w/MM

If going with the multi-melta then I would very much advise a drop pod in order to get him in range asap. Otherwise I would suggest trying to get him a plasmacannon over the melta. Greater range means he can be shooting sooner, though he wil be less effective against armour at closer ranges.