The Soul Grinder
I hate to say that one of my personally favorite units has suddenly become a liability. Because of the rise of Necrons, many lists should have plenty of shooting capacity to handle AV 13.
Armor ain't what it used to be and Walkers in general got only upgrade of note. The Soul Grinder as a Walker can fire Overwatch, which is cool if anyone forgets how to play Warhammer and charges into the Soul Grinder. (Opponents have tried this before, so I'm not just being snide.) The Grinder can fire the 6 bolter shots from the Harvester and then roll d3 hits for the Str 6 Vomit template no one ever used in 5th. It's strange to me, but there you go.
So if you've gleaned from that Soul Grinders are decent in assault, well, they are. Even against Power Fists and Thunder Hammers, it's still a 5 to glance... except those glances now take away precious Hull Points. Most regular, poorly equipped infantry cannot do a thing in combat against AV 13. Soul Grinders will just win out, given enough time.
Ignoring Shaken/Stunned results as a Daemonic vehicle is far less impressive than it once was. Most things hitting AV 13 have either AP 1 or 2, and the newly revised Vehicle Damage chart makes sure it'll be darn unlikely you'll be stunned and almost impossible to be shaken.
If you insist on a Soul Grinder, then Phlegm is still a must. Phlegm, like all Blasts, should be a better deal now that half-strength vs vehicles is a thing of the past.
And the Soul Grinder does bear a significant resemblance to the Chaos Space Marine Defiler. The difference between the two is really the range of the Battlecannon blast and the AV. The Grinder with a 36" range is intended soon to be in your opponent's face, smashing it. The Defiler, a bit more fragile at AV 12, has a range of 72". It's best shooting away all game, plus you can add more guns on top of more guns.