Necrons have five Heavy Support options now and since Heavy Destroyers have now merged with normal Destroyers in the Fast Attack section, that leaves more than half the units as new, all vehicles adding to the multitude Necrons now have access to.
Personally I'm unhappy about the rapid moving additions to the army, I've always imagined Necrons as a slow implacable force with limited faster units like Wraiths/Destroyers on the flanks stopping foes escaping or encircling them. With the Night Scythe transporting units and various Jump Infantry and Jetbikes about the whole army seems very different to me, luckily only one of the Heavy Support is quick.
As it'll likely share a box with the Night Scythe when/if GW releases models, the Doom Scythe is similarly very fast with the Deep Strike, Fast, Aerial Assault & Supersonic rules. Unlike the Night Scythe it even has two weapons allowing it to make use of Aerial Assault.
Like all Necron vehicles it has living metal and like almost all it is armour 11 on all sides. As with the Night Scythe is lacks Quantum Shielding tho, rendering it highly vulnerable for its astounding 175pt price tag, so unless 6th edition does change the rules so faster moving vehicles are harder to hit I'd advise not using it.
Some people however will not think much further than its weaponry (which are admittedly good). Firstly it is armed with a Twin-linked Tesla Destructor but that will likely be overshadowed by its aptly named Death Ray.
The Death Ray is fired by selecting a point within 12", rolling 3D6 and picking another point within that many inches of the first. You then draw a line between the points and for every model under the line its unit takes a Str10 Ap1 hit!
This'll come across as amazing and if the enemy clumps together it will be, on average you'll have a 10" line and only one end of it needs to be near the Doom Scythe. However most of the time you'll be lucky to hit two vehicles or more than half a dozen infantry, which isn't much better than a large blast marker.
For the points, I just don't see it performing well at the moment. Especially as it will certainly be shot down the moment it has moved close enough to fire its Death Ray.
Another vehicle I expect people will get so caught on its weapons and disregard other thoughts, not to say it is bad (The Doom Scythe certainly isn't bad either). While not fast, the Doomsday Ark does have Quantum Shielding and the potential for longer range which makes it a less risky choice than the Doom Scythe, at the same points cost. However it is Open-Topped so if its Quantum Shield is beaten it will be in trouble.
Like the Ghost Ark it has a Gauss Flayer Array on each side which can target units separately from each other and the Ark's main weapon, but since its role will usually involve it keeping distance and facing the enemy these will likely be forgotten in general play. The Ark's main weapon is the Doomsday cannon which is a name I'm less fond of.
The Doomsday cannon has two profiles, one quite powerful and the other much weaker. Unlike other weapon-mounted weapons in 40k its different profiles are used depending on whether it moved or not, the fluff for this is the cannon requires so much of the vehicles power that using the power for anything else (such as the engines) weakens the cannon. The weaker profile is 24" Str7 Ap4 with a small blast, while the more powerful profile is 72" Str9 Ap1 with a large blast.
The reason I put the weaker profile first is that with a limited 45 degree firing arc, I can imagine you having to adjust the Doomsday Ark's facing at least once during a game which counts as moving weakening the blast. This drawback alone puts me off the vehicle before considering that it isn't Ordnance.
With its 90pt price tag, the Annihilation Barge can be seen as the little cousin to the other Heavy Support options (I've not got to the Monolith yet remember), however it perfectly matches the Doomsday Ark defensively and arguably beats it since its smaller model and higher mounted gun gives it an edge at gaining cover saves.
Weaponry-wise it has a either a Tesla or Gauss Cannon as well as its main weapon, a Twin-linked Tesla Destructor and it is on this weapon I'll take the time to talk.
It is possibly that many of you have faced Autocannon Dreads since 5th edition since they are great for punching through transports, injuring Monstrous Creatures and even badly bothering infantry units. Well its shorter range and Ap aside the Tesla Destructor does all that and more. 24" isn't a bad range in 40k and for 90pts with front/side of 13 (even if just while its shield last) you shouldn't be too concerned moving the Barge towards mid-field and while its Ap- limits its ability to break transports it'll still suppress them perfectly well and the chance of additional hits due to the Tesla rule should balance things out, with the hits on nearby units as an extra bonus.
Why is the Annihilation Barge my favourite of the Heavy Supports so far? It is far cheaper than an autocannon dread with superior armour, while outstipping it against most Infantry, Monstrous Creatures and even suppressing vehicles (which your Scarabs can than happily land on and terrorize!).
Probably one of the more recognisable things in 40k (every player will likely recognise a Monolith even if they can't tell Eldar vehicles from each other or Tau ones) and most certainly one of the first things to come into peoples minds at the mention of Necrons. This is rather unfortunate since the vehicle is far less impressive than it used to be, perhaps GW decided that since so many players own them they'd push players towards buying other Heavy Support options..? (Okay, I'll admit to being a little bit of a cynic).
The Monolith is only 200pts now, yet with the change to Living Metal it is now vulnerable to Melta weapons and Monstrous Creatures which is unfortunate as its weapons are short-mid range. It has kept its ability to Deep Strike (in fact if placed in reserve it has no option to arrive otherwise), but can now suffer a Mishap like normal units. In addition it is the only Necron 'tank' and has the 'Heavy' type which is so far unique to the Monolith and restricts it to Combat speed but allows it to count as stationary when shooting, which doesn't actually do anything currently if you look at its weapons.
The only real beneficial change is that the Monolith can now use its Eternity Gate and its Particle Whip in the same turn, but since the Particle Whip is Ordnance its shooting is limited whether it would count as stationary or now. The Whip itself has dropped in strength to Str8 Ap3 but has kept its large blast and 24" range.
If not firing the Particle Whip (perhaps because as a weapon it can now be destroyed) the Monolith has its four Gauss Flux Arcs, which can each fire three Str4 Ap5 shots at different units. Since these are defensive weapons they'd be able to fire at Combat speed anyway, even if also firing its last 'weapon'.
Its last weapon? The Eternity Gate! It can still bring units from reserve or elsewhere on the board to it (even units it couldn't before although be careful with Scarabs and other large based things that will have trouble getting within 2" of the gate), however doing so will not grant any repair bonus now.
Its weapon use is rather strange, it is powerful in that all hit must pass a strength test or be removed from play yet its range is randomised at D6", which means that unless previously assaulted it has a 1-in-6 chance of the enemy always being out of range.
As well as the name change, Canoptek Spyders have been boosted considerably since their last edition. Their downsides are one less attack and while you can still take up to three as a single slot they now remain as a unit instead of being independent, however in exchange for that they have gained +1 Ws, Bs and a wound (I'd rather a wound than an attack with these any day), while dropping in cost by 5pts!
As before they are Fearless Monstrous Creatures and have the ability to create Scarab bases. These must be attached to a unit of Scarabs within 6" but at least allows the Scarabs to make use of their movement etc, as before each swarm has a 1-in-6 chance of causing a wound to its Spyder creator yet this is less of a worry now they three wounds.
Wargear options have changed, they may not exchange an attack for a ranged weapon but for 25pts a Spyder may gain one with 24" Str6 Ap5 twin-linked blast. Its second wargear option costs 15pts and allows the Spyders unit and friendly units within 3" (yes 3" I'm hoping its a typo but tis unlikely) to nullify enemy psychic powers targeting them on a 4+ which is perhaps interesting if you've multiple of them. Its last option and the only one I'd consider is the cheapest, it costs 10pts and allows the Spyder to repair to repair Weapon Destroyed & Immobilised results similar to Techmarines. While this could be useful if you have a couple of the other Heavy Support units (many of which suffer if you destroy their main weapon), I'd only really consider it for its low cost to allow a wound allocation advantage.