Looks like rules are leaking for the new Fortification options, one of which is the Plasma Obliterator:
For basically the price of a Land Raider, you get a medium building with normal access points/firing points and an emplaced Plasma Obliterator turret. This is basically a giant plasma cannon (surprise, surprise!!) which shoots a S7 AP2, Primary 1, Massive Blast (i.e. 7” diameter pie plate) shot up to 72” each turn.
This is a pretty solid choice already, but where I think it really shines is when used in conjunction with the new Khorne Daemonkin codex. Given that this army is, naturally, very melee focused, it stands to reason that it would benefit greatly from long-ranged, low AP fire support as its bloodthirsty (literally!) hordes rush forward.
But the forces of Khorne have a secret weapon up their sleeve… the Herald of Khorne. At only the price of 2 PFs and a MB base, this is a very cheap HQ with a good combat profile and solid buffs to any unit it joins. What most people don’t notice, though, is that the Herald comes with BS7 stock.
That means you can put him inside the Plasma Obliterator fortification and man the emplaced Plasma Obliterator turret, allowing it to use his BS7. In turn, that means that the massive S7 AP2 blast can only scatter a maximum of 5” and, on the statistically average scatter roll of 7”, doesn’t scatter at all. In other words, the Herald make the Plasma Obliterator hyper accurate.
Taken to an even more extreme level, take two Khorne Daemonkin CADs, with two Heralds of Khorne and two Plasma Obliterators…. All of this comes in at a bit over 600 points, but gives you amazingly powerful and accurate fire support starting turn 1 and you still have about 1300 points to flesh out the rest of your Daemonkin army (i.e. Maulerfiends, Jugger-Lords, Cultists to take objectives and/or die for Blood Tithe points, Bloodthirsters, Khornate Terminators, Khornate Spawn, Heldrakes, Skull Cannons, etc.).
Overall, this can make for a competitive melee-based army that still have a very solid (and dangerous) firebase to support it.