Immortals loads of them, give them Telsa. sit back and enjoy. Take a squad of warriors for tanks (that's right) with over-watch Telsa kicks the crap out of anyone. As getting a 6 is beneficial anyway, on the over-watch it can be devastating. It can wipe out the squad before it gets there.
Necrons in this edition would have to really try hard to lose a battle. they've become a very forgiving army. you can make loads of mistakes and not be punished for it.
They aren't that forgiving as even the dedicated CC units can easily be swept in CC (low initiative) or just shot to death (unless you're dropping 400 points on 10-man squads). Also the medium-low range can hard to work with.
Warriors and Immortals make excellent troops. I don't suggest giving all of your immortals Tesla though as Gauss Blasters are still really nice. Depends on how many of each troop you take.
As far as an army core you can't go wrong with Immortals, Large warrior squads or 10 of them in ghost arks, Overlords/D-lords with rez orbs and minch shackle scarabs and Annihilation Barges.