Up coming battle: 1500 points vs Orks

I called this my "Fail List" but loosing is not what I intend to do.  The Sisters of Battle update actually lost more than few options with fewer unit choices, greatly reduced wargear and "simplified" rules. There has been much wailing and gnashing of teeth over this, and I have done more than my fair share.  However, I believe that what is there is viable.  My opinion so far is that making an army with the various choices we have and actually taking as many different units as we can is not only NOT an instant fail, but may be a beneficial tactic.  If you can not have many options to build with, why not maximize the options you put on the table?  Of course this idea may change with experience, but for now, that is what I am working on.

If I remember correctly (ha!) and/or I don't change something at the last minute, I will be taking the following list:
HQ
- Canoness.  No options.  Plane and bare.
- Priest w/ bolt pistol and chainsword
ELITES
- 5X Celestians Squad w/ flamers
- 9X Sisters Repentia Squad (8 repentia and 1 mistress; this leaves room for the priest to join the squad in a rhino)
FAST
- 6X Seraphim w/ dual flamers, dual flamers, evicerator for the superior
- 5X Domions in an Immolator, melta, melta, twin linked heavy flamers on the Immy (my only "ork opponent" driven choice)
TROOPS
- 10X Battle Sisters in a Rhino w/ multi-melta and flamer, combi-flamer for the superior
- 10X Battle Sisters in a Rhino w/ multi-melta and flamer, combi-flamer for the superior (rhino loaned out to the Repentia)
HEAVY
- Exorcist
- Exorcist
- 3X Penitent Engines

What I expect to happen:
The orks will go after the Immolator with a vengeance since that twin-linked heavy flamer can cause a ton of hurt. 
The penitent engines will need a squadron of three for on to survive long enough to get into combat, but will be devastating once it closes.  If my opponent realizes there are two independent heavy flamers on the PE, he may leave the Immolator alone for a turn or two.
I expect the Celestians to be an over-cost, under-manned basic Battle Sister squad.
I expect the troops to cause a lot of casualties in shooting before being swarmed and taken out in close combat. (like always, this has been the norm for years)
I expect the Seraphim to be the stars of the night if I can keep them from being over powered.  1 squad vs 1 squad they will shine, especially if they have the jump.  But if they get multi-assaulted on the orks turn they will fold just like anyone else would.
If I can get the Repentia in the right place, they will cause some havoc and open up killer-kans with ease.  I may have to use them as a boss killer, in which case they will not last long but will get the job done.