My plasma cannons worked a treat, but the stupid reanimation of a 4+ and some took rerolls which Im not sure if its legit or not. One round two plasma shots killed 10 Warriors and they all got back up...Sounds like the plasmacannons should have taken their toll. And try to take larger squads, ravenwing. They should reach melee then.
I do like the Sisters of Battle and really want an update to occur to the current edition so I can play them as a second and most likely primary army. I plan to add two Predators to my army, one with Autocannon/Heavy Bolter and one with three Lascannons to go vehicle hunting. I might add a sister allied detachment with a Cannoness and some Heavy Bolters/Heavy Flamers.I'm still yet to win against Necrons with my Sisters and my Dark Eldar. I'm getting closer with my Sisters. I don't play Marines but the weapons of Sisters and Marines are pretty much identical. I'm having a bit more success adding in more Heavy Bolter and Heavy Flamers. Don't know if that helps you as Dark Angels though.
He always hides his tomb spider out of sight of anything so I can't shoot it whilst his wraiths are out clawing my tactical squad and independent characters to mulch. Else I'd shoot it up to the point where it resembled cheese of the highest swiss calibre. His Wraiths reanimation protocols and the fact that his units aren't just powerful but stupidly cheap mean it's so difficult to fight Wraiths with what I currently have.Killing the Tomb Spyder first will remove Reanimation Protocols from the Wraiths, taking them down from 'borderline broken' to 'very powerful'. Rad Grenades are also a big help against them.
I would say give me a few more games against them and I'll come up with something (having just completed 1500pts of Space Marines, who are similar to DA), but since the only Necron players I know have quit the army due to the new Codex, I don't think I'm going to get much experience against them.