Sisters are probably the best army in the game at any point level when it's a pure Sisters army. Acts of Faith are downright ungodly-- the Cleanse and Burn maneuver with a Dominion squad armed with flamers is just mean, and assault-oriented units like Sisters Repentia and Seraphim ignoring armor on an act of faith (not that the Repentia need it, but there are other things they can do that are just as mean.) is awesome. Exorcists are quite possibly the best anti...well, anything... tank in the game, too... multiple-shot AP1 krak missiles? Count me in.
I'd ditch the stormtroopers and the Inquisitor, and load up on Sororitas. I think the list I usually fight is something more or less like this:
HQ/
-Canoness armed with a power weapon and inferno pistol; jump pack, litanies of faith, rosarius, cloak of st. aspira.
Elites/
No Selections
Troops/
-Sisters of Battle Squad, 15-strong. Attached Priest with Eviscerator, Sister Superior with bolt pistol and power weapon, two storm bolters, Imagifer.
-Sisters of Battle Squad, 15-strong. Attached Priest with Eviscerator, Sister Superior with bolt pistol and power weapon, two storm bolters, Imagifer.
Fast Attack/
-10 Seraphim. Sister Superior with eviscerator. Two twin-linked inferno pistols.
-10 Seraphim. Sister Superior with eviscerator. Two twin-linked inferno pistols.
-Dominion Squad, 6-strong. Imagifer. Four flamethrowers, two bolters.
--Immolator AFV. Extra armour, twin-linked heavy bolter
Heavy Support/
-Exorcist with Extra Armour
-Exorcist with Extra Armour
-Retributor Squad, 10-strong. Four heavy bolters. Sister Superior with storm bolter.
Now, that may look like an outrageous amount of anti-infantry fire, and it is... but the thing is, you can turn a lot of that stuff into AP1 fire with Acts of Faith, and coupled with heavy bolters and other high volume of fire weapons... whatever doesn't get torn up by the bolters gets chopped in close combat with the Seraphim. The two Exorcists only have to survive long enough for the seraphim to get in close where they can hop in and out of combat, shooting those inferno pistols at any tanks that happen to threaten them. The Immolator full of Dominions with flamers usually hangs out in the back, in cover, so that if something goes wrong and the Sisters are being pushed back or not breaking through, it can zip forward and use the Cleanse and Burn maneuver to basically unleash a torrent of AP1 flamer fire. For those of you not familiar with the Cleanse and Burn maneuver, it's basically where you have an Immolator packed full of Dominions armed with flamers bail out, use an Act of Faith to make their weapons ignore armor, and bake whoever's unfortunate enough to be within 10'' (as you can disembark 2'', and the flame template is 8''.) Then the immolator adds its fire in afterwards just to seal the deal.
It's one of the few armies I actually have trouble fighting on a regular basis. They just sort of smoke you through Acts of Faith. Never made much sense to me since the Space Marines are by far holier, but hey... it's all in good fun in the end, I suppose... and the jokes about nuns with guns never get old.
