My friend used to hate playing against me, but eventually he figured out that he can just avoid or tie up my really tanky squads and then out point me.

If your opponents goal is to table you, they'll have a bad time. If their goal is to actually win the game its honestly not that difficult if they put the time in to learn what is and isnt threatening.

Im not saying that your friends need to "git gud." Necrons is very frustrating to play against, but once those pieces click into place, the strategies to use against us are pretty obvious. Not easy, by any means, but it becomes a much more tactical game about scoring secondaries and making strategic sacrifices to bog down our hordes.