Well had a good play with the necrons so far and come up against them in skirmish - quite fun to play.
Tip for these is one of the commanders "relics" (from a tier 2 building with tier 3 upgrade) the "resurrection stone" this will res all dead necros in an area around the commander and currently (not sure if bugged) ignores the unit cap. You can basically keep a steady stream of cheap units running into same point of opponents base defense then walk the lord over and res them all.
Tip for these is one of the commanders "relics" (from a tier 2 building with tier 3 upgrade) the "resurrection stone" this will res all dead necros in an area around the commander and currently (not sure if bugged) ignores the unit cap. You can basically keep a steady stream of cheap units running into same point of opponents base defense then walk the lord over and res them all.