At first, the Tyranids seem like a daunting army to fight against with Necrons. These fears are mostly unfounded and I was pleasantly surprised at how well these two armies matched up to each other, so I've decided to post what I've learnt. Please bear in mind these experiences are from a small game of 40k without any vehicles (800 points each side) so these experiences may not match bigger games.
- Unless you plan to march your Immortals forward against the Tyranids (which I seriously don't advise), equip them all with Tesla Carbines. As they are 24" assault weapons, they have a serious advantage over Gauss Blasters at long range and far more potential on the number of hits you can score. As Tyranids use no vehicles what-so-ever, you'll find no tactical advantage with the Gauss Blaster other than the AP value, and you'll be wanting hits over no armour saves. Tesla Carbines also always get 3 hits for every hit on a charging unit whilst overwatching.
- Don't underestimate the usefulness of the Phaeron upgrade for Overlords. If you take it, put them in a squad of Warriors (it's a useless upgrade for Immortals with Tesla Carbines). In a "charge or be charged" situation, it's always a good idea to pound the opponent with gauss fire then charge for +1 attack, which you can do with the Phaeron upgrade. You could risk overwatching, but I find it's less useful than an extra attack.
- Wraiths should always be equipped with Whip Coils and thrown at the enemy for two reasons. Firstly, Tyranid players tend to underestimate them in close quarters and secondly, as Tyranids are less of a shooty army so there's less risk of them being shot down before they can shine. With invulnerable saves and rending attacks coupled with S4, W2 and A3, they are vicious, and the Whip Coils allow you to strike first against most of the combat. I was able to kill a brood of Genestealers, make a Venomthrope run away and landed the killing blow on a Hive Tyrant with mine. Which reminds me...
- Watch out for Hive Tyrants. Seriously, there's no shame in these guys not having an invulnerable save. I lost my Overlord, 15 Warriors and 2 Wraiths against this monstrosity, whilst I only lost a single Immortal otherwise.
- Reanimation Protocols. Very useful. Don't rely on it.
- Warriors and Immortals are terrible in combat, but Immortals at least are less killable. Unless you're sure of a win, keep them out of combat as much as possible...
- Overlords on the other hand are far more durable. With T5 and S5, they can give a surprising number of Tyranids a run for their money, especially if they have a Phase Shifter. They won't stand a chance against Hive Tyrants however. Nemekh the Summoner got squished without a second thought.
- Choke points. If they exist, use them, and stand well away from them. It's all very well mowing down Tyranids as they struggle to all get through, but if they charge you, you won't be able to shoot at the waves coming through.
- Quantity over quality is definitely key against Tyranids. If they have to split their charges, they become easier to kill.
Well that's all the nuggets of wisdom I have for you all today. I have more games planned and I will update with what I've learned. I will test some more into Mindshackle Scarabs (using the lesser known tactic known as "stop hitting yourself") and Tesseract Labrynths. My Mindshackle Scarabs didn't work this time around and Tesseract Labrynths seem the best bet to kill my nemesis: The Hive Tyrant. If anyone else has anything to add, please do not hesitate to comment!