Summary
The soul grinder is not the best unit. It suffers from the 'hybrid tax' that
GW places on all units that are good at multiple things.
It's not the worst unit in the codex -- that dubious 'honor' still goes to screamers. If were to want to find a place for them, it would be units that are just simply hard to kill.
Below I tried to cover the good and bad of the grinder.
The Good : Punching Tanks
Iron Claw is actually quite good against tanks, with
damage ratios of a 64. While not the best damage ratio, it comes on very durable platform.
Basically, it's going to be hitting 1.5 times at 8+ wounds or 1 time at 4-7 wounds. When it hits, it will be wounding on a 2+ with a -3 to Save and
d6 damage. That's not bad at all.
The Good : Tough
Tough. Nurgle is the way to go with these guys -- unless you have the changing nearby. Even still, I would run these guys as Nurgle with the tallyman - which lets the reroll 1s to hit after 2 enemy units are killed. Hitting 58.88% of the time instead of 50% of the time helps.
IMHO I've also found that a 3+/5++ with DR is better than a 3+/4++. Often you will be getting your 3+ save, and that DR stacks. The 4++ 5% less effective off the top, and is useless against bolters.
14 wounds is a bear to remove. Since you are taking Nurgle, that's the same as 21 wounds on a Khorne Grinder. A Nurgle caster nearby can also throw d3 wounds back on it. They can be killed, they just take a lot of firepower to do so.
Compare them to a knight at 24 wounds for twice the price. That's the best thing these guys have going for them, and they are built tough.
The OK: Punching MEQ
The warp claw is the way to go with these guys every time. Doubling the attacks to 6 attacks is very good.
STR 8,
AP -2, D3 wounds is actually pretty darn good and will be wounding marines on a 2+. The D3 wounds means it's extra good against bikes.
That said, it's no daemon prince, who has more attacks and hits 35/36 of the time.
The OK: Guns
If the grinder could hit on a 3+ and could move and shoot heavy weapons, people would be saying the grinders are
OP. That's because these guns are actually rather good.
The harvester cannon is an autocannon that has 1 extra shot, and the Phlem is great against armor.
STR 8, -2
AP, 3 Damage is just bad news for vehicles.
But the problem boils down to the same issue -- hitting on a 5+ sucks. Even a nearby daemon prince will not be that helpful. You often will just forego shooting all together to advance.
If these weapons were assault, they would be perfect -- but someone goofed here. The fact is you always want your grinders in smashing someone's face and not sitting and shooting.
The reason the guns are in OK and not bad is because you can actually use them and hit on a 5+ -- it's just a nice surprise when it happens.
The OK: Movement
8" move out of the gate does not suck. If you are advancing you should be engaged by turn two. It's not as fast as a helldrake, but it is as fast as bloodcrushers.
The grinder does not hit nearly as hard as the bloodcrushers, but is a hell of a lot harder to kill.
The Bad: Hitting on 4s
This is just horrible. I hope
GW fixes this in the codex release
The Bad: 3 Attacks
I get that the grinder is a 'tough unit' and not a 'glass cannon' but it's damage output is still lacking
IMHO. They should have given it 4 attacks.