Okay, I don't really have that much experience with sisters at higher point totals, but here are some points I'd put some thought into:
- Jakobus is only 30 points more. You lose a bit of shooting and combat capacity, but that shouldn't be a big deal as you'll want them for their supporting abilities anyway. Also, they both give hatred and fearless, respectively to their unit and everything within 12". Just 30 points extra gives you: counter-attack for everything within 12", and extra
AoF for his unit, a better shield of faith, and also with his rosarius he has a far smaller chance of
ID.
- The
BSS should probably have heavy flamers. It'll make them much more reliable for clearing the enemy off objectives, as well as keeping them with the overwatch.
- It might be worth it to take a dominion squad with four meltaguns. Your anti-armour is all strength 8, and the multi-melta's probably won't reliably get close enough to deal with any
AV 14 that might show up. Outflanking dominions excel in this role, and on top of that they'll often hit side/rear armour.
- Get storm bolters on the exorcists. 5 points gives you an amazing save against
weapon destroyed, which is bound to happen sometime.
- I'd get at least one immolator with a twin-linked heavy flamer instead. They are just so much fun to roast hordes with

Also, on a more serious note, it's useful to get a measure of your opponent. If he tries to take out the flamer first, he's afraid of the flamer templates more than of the melta's. Knowing that can work in your advantage.