I have used this list in my last game in a cleanse mission and it seemed to work really well. I am considering on using it in a 750 point tournament coming up this June and I would like some feedback on whether or not you think that it would be effective.

HQ:
Canoness - 136
Blessed weapon, inferno pistol, jump pack, cloak, book, frags.

ELITES:
5 Celestians - 80
Multi-melta.

TROOPS:
10 Battle Sisters - 199
VSS with book, 2 flamers, rhino with extra armour, smoke.

10 Battle Sisters - 194
VSS, 2 flamers, rhino with extra armour, smoke.

HEAVY SUPPORT:
Exorcist - 140
Extra armour.

Pts: 749
Faith: 5
Models: 26
Vehicles: 3

I think you could drop the multimelta on the Celestians. The squad seems really vulnerable IMO. As they are really forced to wait for a tank to come within range of them in order for them to be of any use.

The rest looks good.