There's only one piece of advice I'd really like to give, and it's one that struck me as soon as I saw the list;
I would strongly recommend you go MSU.
The reasoning for that is as follows:
-
GSC are really very flimsy, with only 5+ armour saves across the army and only a 6+
FNP boost from the Iconward. While we can make great use of cover, and hence become survivable, there's plenty of ignores cover around that will simply wipe units out and, even without Ignores Cover, we don't have access to re-rolls or really good
FNP that make a lot of other armies survivable. So, if a Riptide or whatever is removing a
GSC unit per shooting phase, it's best to make it a small unit.
- Furthermore, more units of smaller models mean more chances to roll that precious "6" on the Cult Ambush table, which is really what causes headaches for our opponent. Sure, a unit of 10 Acolytes charging from reserves isn't as bad as a unit of 5 doing the same, but, if your army consist of only units of 10 or of 5, the latter is much more likely to happen. Plus, if you really think a particular unit in your opponent's army needs 10 Acolytes to assault it right off the bat, then you can send a second unit of 5 in.
- Smaller units are also a lot easier to hide, as well as a lot easier to fit entirely into cover. This is useful for a when a certain unit doesn't get the result you want on the cult ambush table and you want to keep it safe for later. Just pop it behind some
LOS blocking terrain and try again next turn. This is especially important for getting objectives. If you place your own objectives behind
LOS blocking terrain or, at the very least, in good cover, you can ensure, with a constant stream of
many units popping in and out of cult ambush, that you'll be able to grab that objective late game or for the maelstrom card you've drawn, and that unit will be safe. It also means you don't have 10 Acolytes worth of points babysitting a home objective.
- It can also be argued that units of 5 gain more benefit from the Cult Insurrection ability to regain
D6 models after having gone back to the shadows. Whilst there's more models to be gained in units of 10, you're not going to restore that unit to full health unless you disappear with 4 guys left (which is silly). If your opponent is unlucky to leave one model in a unit of 5 left standing, he knows he has to kill that one model or else there's a 50/50 chance that unit is just going to come back in full strength, and all his shooting will have been for nothing. With a unit of 10, your opponent knows that at least some of the damage he's done to that unit is permanent (unless you spend 4 turns bouncing in and out of cult ambush that is)
- Going
MSU allows you to take more units and hence more formations. I don't fancy crunching the numbers but I certain that if you split most of your units up into 5s, you'll easily have enough units to take another Subterranean Uprising, if not 2. This is the best formation in the book, so it's worth taking advantage of if you can and maximising the number of units that get that double roll and the Cult Ambush table, and Shrouded on the first game turn. You may also be able to fit in a
CAD or two (depending on how many Subterranean Uprisings you take). Once again, this is a useful way to go as you get a few units with ObSec (which is especially brilliant on
GSC - remember when I was talking about grabbing objectives before?) as well as the ability to take more than one Patriarch, Primus and Magus. This will let you increase your oomph in the psychic phase and/or get another
3D6 with a Subterranean Uprising unit (although this ruling is in contention - not sure if it's been
FAQ'd yet).
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In the spirit of
MSU, I'd advise that, generally, you keep your costs down. You don't need to be extreme about it (for example, Cult Icons and a Rock Saw per squad is always worth it), but stuff like unit leaders, their equipment and familiars not named the Crouchling can be done without in most situations. I don't think leaders are especially worth it, especially when dropping four of them can buy you another squad. The only reason I would (and do, in my own lists) choose to not go
MSU is with the unit in the Subterranean Uprising formation to which you join your Primus. Since that unit has a much better chance of getting to assault from reserve than anything else in your army, it's worth kitting that unit out for combat even more so, with extra bodies and maybe a leader (go with a lash whip + bonesword, as that extra initiative is really worth it to get the jump on the myriad of
MEQs and even Eldar).
However, one area that I'd ignore this advice is with the Neophytes, since their heavy/special weapon options are actually really good. With them, it's well worth paying points for two Seismic Cannons and two Grenade Launchers to make what is actually a very shooty unit (and still for only 100pts). The heavy weapons are especially worth it seeing as you can regain them through "Numbers Beyond Counting".
Finally, your Magus has two artefact things, which I'm pretty sure isn't allowed.
Hope this helps, if you have any more questions feel free to ask!
Just waiting on a 
