This is what I posted to answer a post on my favorite Warhammer 40K blog Fritz40K.
My thoughts on getting my 'Crons on par with the 5th 'dex boys:
We’ll Be Back – Love it, no need to change it.
Phase Out - Let it stay for standard games, but for some special games like combat patrol, lift it.
UnNerf Gauss - I want something more fluffy that just giving them rending, don't want to lose the fluff. Against non-vehicle targets, on a to wound roll of 6, automatic wound regardless of target's toughness and counts as an AP1 weapon. Against non-vehicles, an AP value of 1 is no better than an AP value of 2, because no armor save is better than 2+. Against vehicles on a roll of 6 to penetrate the vehicle's armor, automatic glancing hit unless it would be a penetrating hit, with the weapon counting as AP1 again. Against vehicles, an AP value of 1 has value, adding +1 to the vehicle damage result roll, allowing gauss to at least wreck on a glance, and making penetrating hits more lethal. This option would help get the 'Cron's anti-vehicle closer to 4th ed and help them deal with their lack of weapons options (i.e. no meltas, and krak type weapons). Another option is to just give gauss a +1 on the vehicle damage chart with glancing hits or just let the 'Crons have penetrating hits on a roll of 6.
The lack of power weapons - I think it would be easily addressed by modifying the disruptor field (DF)war gear. Make DF work in close combat again non-vehicles as well, counting as power weapons against non-vehicles. Of course whatever correction is made to gauss regarding glancing hits on vehicles would also have to be applied to DF as well.
Lack of mobility – To counter the increased mobility of the other 5th ‘dexes, the ‘Crons need more units that can DS or infiltrate in, and teleport. Also, ‘Crons need a DS scatter of only 1D6, their technology is too advanced to scatter 2D6, doesn’t meet their fluff. This I will talk about more in unit descriptions.
C’Tan – To make up for not have psykers and their new crazy 5th ed powers, the C’Tan need new, more powerful offensive attacks similar to the new powers the psykers are getting. Also, the new armor saves and invulnerability saves some of the characters are getting in 5th, the C’Tan need their invulnerability saves increased to at least 3+, they are gods for crying out loud! They also need more mobility, they need to be able to DS around the board as if they had VOD and should also have the Monolith’s ability to force models away to make room for them.
Lords – We don’t need cheaper lords, no bronze, silver, gold stuff, stupid bad idea; the current lord should come down in point cost a little. If you want a cheap HQ alternative, there should be an elite pariah HQ choice with a little better stats than the regular pariahs. What we need are special lords like the other armies have. Examples would be a wraith lord with the option to take wraiths as elite and fast attack choices, or a destroyer lord that does the same, or others that let you take flayed ones or immortals as troop choices. Then we need lords in between the current lord and C’Tan. The fluff talks about lords crafting bigger better bodies for themselves.
Immortals – This guys are great, other than lower point cost, maybe increase I from 2 to 3 and A from 1 to 2, but not really needed.
Flayed Ones – These guys need to be more like the Space Marine Vanguard. They need their A increased to 2 if they increase the max unit size to 15 or more, or to 3 if they don’t. And if DF ends up at ignoring armor saves, awesome close combat unit. Also, they should probable be a troop choice.
Warriors – Lower point cost, no other chance if the above gauss and DF changes are made.
Wraiths – These need to be the ‘Cron CC Termies. Need to increase max unit size to 5, and there attacks need to ignore armor saves (build in DF from above). They also need DS.
Destroyers and Heavy Destroyers – I think these two should be merged. Make their gauss cannon a dual pattern weapon, cyclic fire same stats as gauss cannon, focused fire same stats as heavy gauss cannon. And a question on their T: If they are immortals that have toughness 5, basically on a jet bike, why did their toughness not increase to 6 like the lord with a destroyer body does? They should be a T6. I would place point cost between the current destroyer and heavy destroyer. Unit size 1-4, fast attack or heavy support choice, that why you can still only field 24 total destroyers as you can now.
Scarab Swarms – Not sure why everyone wants a larger unit size on these guys, but I guess that would be fine. Lower points cost a point or two. With the DF mod above, they would be CC killers.
Tomb Spyder – Don’t think I would change this one. Maybe let it repair a Monolith, the Necron version of a tech marine or Mek, with bonuses to repair rolls for attached scarab swarms.
Monolith – Originally I was not going to change the Monolith, but after see the rules for the Space Marine Caestus Assault Ram, that costs the same 235 points, the Mono does need an upgrade. To bring the Mono in line with the new Ram, the Mono needs a 5+ invulnerable save, the ability to teleport about the board as with VOD, Particle Whip needs AP1, and the old rule of units disembarking from a Mono count as disembarking from a stationary vehicle so they can assault out of the portal again.
As for new units, I would like the ones mentioned in the Lord section, maybe a new C’Tan or two, and a new heavy support like a bigger tomb spyder. Maybe a ‘Cron drop pod, a stationary portal that DS’s in, no weapons needed, just increases mobility, make it a dedicated transport type option to not take up org slots.
My thoughts, and I love Necrons so I have thought about it a lot.
I did forget to add that the Flayed Ones should be able to assault after DS'ing like the Space Marine Vanguard.