Some people might say, that currently Necrons are barely playable, that they deserve more buffs, they are so weak. Well, no. Right now they are very strong and abusable. But if you remove current meta, they could probably end up too weak. So, we need to think in advance.
But first of all, for the love of some resemblance of balance, remove/rework Mass Recall. Currently double Cairn plus any Light Cruiser as constantly invisible flagship is the meta, and it's an extremely abusable one. It's basically 3 jumps in a row, and if you can't kill flagship very fast, you are so dead. Necrons can chase down ANYTHING and run away from anything if they need to. Considering huge DPS and burst potential of Necron ships(as well as a huge morale shock plus boarding), it makes them extremely deadly.
If you could crit flagship bridge and take it out of invis, it would be great, but guess what, necrons have TWO ways to ignore bridge crits, so this is a no go. You can try to use escorts to try and spot it, but it just delays the inevitable and puts your escorts at risk. So, unless you can play perfectly against an invisible threat, your chances of winning are pretty slim.
So, at the very least, if using Mass recall would take 5 seconds and would disable enemy flagship for the duration(may be even Mark it), it would be at least tolerable. Necrons would still catch up with you, but hey, at least you can damage enemy flagship in the process and run away much more easily instead of suffering a lot of burst damage instantly.
Second, let's talk about the Starpulse wave. Right now, even if you have only 2 of those, they simply deny any kind of ordinance play. Necron have turrets, bomber fighters, jump, and then even Starpulse on top. I'm not sure if Necrons really need it to damage enemy ordinance, but at the very least there should be a limit on their uses, cos they are insta killing things, that do have limited uses(like bombers or torpedoes), cos right now, together with other counters, it denies any ordinance play completely. And it makes them much harder to kill than it's nessesary.
Trirdly, Necrons are really one dimensional right now(Recall, attack, jump after, destroy or jump, attack, retreat by Recall, repeat) and need some different playstyle. But alas, here I have no ideas about what to give them.