I think that if you did everything that Jaggedtoothgrin suggested, the Necrons would become an army that wins a lot more games than it loses.
As a background to my comments, I've played over 30 games with Necrons in the last 12 months. I absolutely do not claim to be the world's best Necron player - they are a hard army to master once your opponents figure out how to keep them away from important areas/formations.
By the nature of the army, Necrons tend to win big or lose big - there are very few draws with the undead metal zombies. I like this and I don't believe that too many changes are required to make/keep the list balanced/playable and fun (for both players).
I particularly struggled against massed air formations of Ork Fighta Bommerz (especially when the Speed Freek list was designed to beat my Necrons during a campaign game which is fair enough as I designed my list beat him

). 6 formations of Ork FB's basically guaranteed my Orb would be broken. Even so I still made a game of it and we both played a memorable game. With JTG's suggestions, I believe I would have won easily against an army that was designed to beat me.
I like some of the suggested changes and I get why some think they are necessary but I think they would make Necons unbalanced and too powerful.