Wow, a few corrections for you.
Tomb Blades can be 3+armor, S6 ignores cover small blast units and are MUCH cheaper
Tomb Blades could always be upgraded to be AS 3+ and not MUCh cheaper, however, all the UPGRADES have gotten much cheaper by 80%! Oddly, you can't fully equip them like before. You have to choose between Ignoring Cover and boosting your own cover. More importantly, and this is rare in the Necron army list, each Tomb Blade can be equipped with different equipment, allowing for a combination of Tesla, Gauss, and Blast. They are also a minimum of 3, but can be fielded in squads of 10.
Triarchs are cheaper.
Oh, yes, they are, by a huge degree. Range of Rod increased and the Rod is no longer Unwieldy. The Voidblade has a better AP, but the Entropic Strike took a bit of a nerf to being a version of the old the Disruption Fields now.
Wraiths are AMAZING for their points (BEASTS, ignores cover, T6)
T5, actually. Not as good as T6, but definitely better than T4.
Decurion detachment give buffs to RP rolls
Yeup, but you lose Objective Secured. The size of everything makes for HUGE options, but the Formations can be large and clunky if you don't plan well. But if you do, the force can be quite powerful.
Only one Warscythe per army
Um, nope, you're thinking of the Relic. Warscythes are under the Melee Weapons list which any Overlord, Lord, or Destroyer Lord can have. Also Anrakyr and Obyron both carry Warscythes.
Tesla bonus doesn't work on snapshots
Yeah, but rather expected.
Scythes of both kinds are much more expensive
Night Scythe is more expensive, but the Doom is cheaper.
The Doom's Death Ray is no longer a Beam, but a Blast, but gained Lance in the bargain.
The Night Scythe can no longer carry Jump Infantry or Bikes, it's just a regular one-way Transport now.
MS Scarabs cause... a fear test. In challenges. Yeah...
Yeah. The actual finished product is actually pretty poor. The occasions where you will really want it will be useless 75% of the time. Now where's that Farseer or Ethereal to Challenge? Forget about using against them against Marines.
Bargelords can't rotate wounds/saves as before
What? Bargelords are still Chariots and that part hasn't changed all that much. They HAVE gotten better by giving a morale bonus in an area, and the Phylactery gives IWND to both Lord AND Barge. The Phase Shifter, also nerfed to an Iron Halo, only affects the Lord.
Still the same. I can't say about the pre-3rd version, but the last two versions of Scarabs have been WS 2. Still Entropic Strike was changed from being an Armour Stripper to being just Gauss in melee.
Destroyers have 2 wounds... and are JSJ infantry (like XV8s)?
Indeed. Weapons haven't really changed for them (Heavy on a Relentless model may as well as be Assault), but every Tau player knows how useful it is to Jump back in to Cover or Hiding.
However, Destroyer Lords are also JPI, and so make keeping up with Wraiths and Praetorions difficult. They do make great candidates for working with Flayed Ones, though.
Some other thoughts:
Reanimation Protocol is FNP+. Will work against Instant Death, but is reduced by it. This can be fixed by having the unit in a Decurion Detachment or in a unit with a Cryptek. Doesn't work with Feel No Pain (but not a lot of sources of that in this codex, surprise). This will actually make it stronger by helping to prevent Morale Checks that would cause a unit to run away from the fallen from Shooting or cause an Assault Loss to trigger a Sweeping Advance.
Quantum Shielding now ignores Lance indirectly, but is nerfed for the Forgeworld Tesseract Ark.
The Nightbringer can really hurt a low Ld unit, and may be able to destroy a Swooping Flyer with a lucky glance (and I'm not talking Snap Shot lucky).
A lot of people have been confused with just how the Decurion Detachment and some of the Formations work, so may accidentally (or obfuscate to) cheat with them. The same could be said with the Powers of the C'tan.
A single Decurion CAN field either 40 Doom Scythes or 10 Tesseract Vaults in one Detachment, though, after fielding a Lord, 2 Warrior units, an Immortal unit, and a Tomb Blade unit. More if you double up on the Lord/Warrior/Immortal/Tomb Blade list. If those didn't require Apocalypse point-levels to bring it to the table, it would be horribly broken.
Crypteks are no longer as flavorful or powerful, can bring some interesting things to a unit, like increasing their RP roll or providing a 5+ Invul, but aren't as "must-take" as they used to be. They can be your sole HQ in a CAD or AD now, though.
Over all, this codex seems to be built around using the Formations and Decurion Detachment to replace a lot of things that used to be Wargear for Lords and Crypteks. Some of the combinations can be a little nasty, too, but the bulkiness of some of them hold back the power just enough, I think.