Battle Sisters
This is going to be the pretty standard 10 Battle Sisters with two meltaguns and rhino for 180pts. Add in a combi melta for 10 additional points and you have your unit. This will be pretty standard I would think in most armies. So there you have 720 or 760 of your basic army when you take at least 4 units.
(Added Info)
Battle Sisters start with 9 Battle Sisters + 1 Sister Superior for 125pts. They do come with flamer options, including a heavy flamer. You can also add up to 10 additional Battle sisters for 12pts each.
I would think that in there somewhere, you have to think about backfield objectives, so switching out one unit with a multi-melta might help out a lot. Most of the variability in this army will be in everything else, besides the troop choices.
Yes, I know you can take 20 Battle Sisters in a unit, and yes this might be a good idea in a single squad, but the standard will 4x 10 Battle Sisters in a Rhino.
The nice thing is that these unit have some flexibility on the battlefield. Breaking them off the board will be relatively hard, as they can have the chance to save themselves with their Acts of Faith.
There is no other troop choice.
At first Glance, the rest of the army is where the variability will come in. Personally I see rhinos as the troop transports, and Immolators carrying everything else with some Exorcist in the back. There is some flexibility in the Elite, Fast Attack, and HQ sections, but it really does come down to a rhino/immolator force with 3 excorcist in the backfield.
The army will consist of a ton of melta, but that is what we expect. The Shield of Faith being on your rhinos and immolators is kind of cool, but really it wont save you enough to get in close. Shield of Faith gives you a 6+ invul save. This is an army that will rush in and unleash its flamers and meltas like before. So like I said, it is pretty straight forward, without a lot of shineys.
That doesnt mean it wont be effective, I still see some very possible competitive builds, and I will get into them more as I get more time.
