well im working on a ravenwing army and i play against a friend that has Nids
For HQ, I wouldn't use anyone that costs that many points, most of the Dark Angels HQs really won't do too much against the Nids. Unless you want to fork up 205 pts for Sammael, Master of the Ravenwing and put him on a Land Speeder (which will do lots against Nids), I would use either Belial or a Company master, nothing much else.
Elites I would just keep it simple and just use Terminators. Add Assault Cannon to any and all terminator squad you have. At most just 2 terms with CC upgrades. Add a Dreadnought as well, points permitting, keep the assault cannon and if you want make any upgrades to anything else on it. I would suggest if any to switch CC arm to Missile Launcher and storm bolter to heavy flamer.
For troops, keep them in small groups to keep the Nids going for mulitiple units so they don't all get to rush at one thing. I think for weapon upgrades I would keep it to just flamers. Melta will only take out one and plasma can hurt you back, and you will need all the men you can have against Nidzilla. Some transports such as Razorbacks are also very helpful as well since you should have smaller groups. Basically just have small groups for small points to maximize points for other elites, fast attack, and heavy support.
With what I have given you won't have much room for bike squads. I would have at most 3 separate Land Speeders with Heavy Bolters and Assault Cannons, making each 100 points. Now obviously you don't have to have 3, and just one can do some decent damage alone. Bike Squads would be points permitting kind of thing.
Tank wise, I would say Vindicator as a heavy tank b/c it will destroy lots of Nids at once. Besides Vindicator, I wouldn't use many other tanks, MAYBE a Land Raider, points permitting, but just as a transport for Terminators or a couple troops and with its Lascannon to take some shots at a possible Carnifex or two, Hive Tyrants, and Zoanthropes.
Theses weapons are your best friends against Tyranids:
Assault Cannons
Heavy Bolters
Flamers
Demolisher Cannon
There you go, my long 2 cents :mrgreen: