Megalodon said:
Necrons really aren't underpowered when done properly, just like any army. Some armies are just easier to run than others (but people still get it wrong).
Let me rephrase - if you deviate from the 3 or 4 units that actually work in the Necron codex, or if you are fighting an opponent who is clever enough to just run straight into CC with your warriors and phase you out, then the Necrons are underpowered.
Play a sole warrior/lord/lith (potentially desty's too) army and only play those who don't understand how the current rules favour CC against the 'Crons, and you'll do well. Potentially very well (especially if they don't understand Phase Out and just shoot the 'Lith).