Effective vs. Crons?

1) Against necrons I would always bring an excorcist, it really hurts anything outside of res. orb range.

2) Necrons generally deploy in blocks around the lord to maximise res. orb coverage, I would spread your forces out a little to try to attack the flanks. It is a very bad idea to charge head on into the blocks of warriors as you will lost to rapid fire.

Destroyers should be prime targets along with the immortals and lord. Wraiths will try to run up flanks and pin down units, do not let this happen for it thay can be a real pain to shift.

I really wouldn't worry about the monolith as its slow, too heavily armoured for you to really hurt it.

Necrons hate power weapons when the lord isn't about so a few won't hurt.

Necron lords are very resilient but aren't that great in combat, if you charge him with anything that is half decent in CC he will probably die, though the lord will either hang around with the warriors or VoD the immortals, in that case they need to die as they will tear your army apart with their guns.

Hope this helps.

*edited for grammar*

Although I'm still trying out different numbers and unit combinations, I was initially planning on a list something like this...

Models: 55
Starting Faith: 7

HQ:
Canoness with Jump Pack, Blessed Weapon, Cloak of St. Aspira, maybe Litanies of Faith

Elites:
Arco-Flagellants X 5

Celestian CC Squad
Sisters X 10
Flamer X 2
VSS with Eviscerator, Book of St. Lucius
Priest with Power Armor, Eviscerator

Troops:

SOB Squad A
Sisters X 11
Flamer X 2
VSS with Eviscerator, Book of St. Lucius

SOB Squad B
Sisters X 11
Flamer X 2
VSS with Eviscerator, Book of St. Lucius

Fast Attack:

Seraphim Squad B
Sisters X 8
TL Inferno Pistols X 2
VSS with Eviscerator, Book of St. Lucius

Heavy:

Retributors
Sisters X 10
Heavy Bolters X 4
VSS with Bolter, Book of St. Lucius

If your opponent has any sense he'll use the Monolith as a pie plate dropper. It's really the only weapon the Necrons have that can hurt the Sisters. They simply don't have any AP3 weapons apart from a few 1-shotters. These don't give any return worth speaking of when all they're doing is killing low point value Battle Sisters. Sheer volume of shots is not effective against the Sisters, they're too well armoured and too cheap. Necron warriors are no match for the Sisters in a close range firefight.

There are three tactics to follow I think. Kill the Monolith, kill the Lord and force phase out. This can be done in any order but I'd be inclined to do them in that one. The Monolith can be taken down best with a pair of Exorcists. The Lord can be slain by a charge from a Canoness and an Eviscerator wielding VSS Celestian or Seraphim. Necron warriors can be DG'ed to death. If your opponent has Heavy Destroyers, Tomb Spiders or a Flying Lord then these are a good target for an Exo volley, ahead even of the Monolith.

Above all you need to as rapidly as possible knock out all the things which support the warriors, using your assault troops and fire support. The battle squads can handle the warriors, but not if they're being subjected to a bombardment while they're doing it. If you ignore everything and just go for phaseout then the Necron player will keep the warriors going with the Res Orb and Monolith, while rapidly thinning your Sisters ranks. Warriors can be a firepower sponge. They're pricey but not nearly as much as other things in the army, and very resilient. Without support though they lack the firepower to defeat an enemy by themselves due to not having any special or heavy weaponry.

I have quite regularly faced crons and to be honest, with what you are describing (lord, immortals, destroyers, wraiths, monolith) I would be rubbing my hands in glea.

He is using a lot fo expensive models here, I would guess that he is probably fielding around 25 or so warriors, which would mean his total army size is around 35 if you kill 24 then you have phased him out. The key then is to kill the easiest 24 you can fins (effectively the warriors. Keys to this are, exorcists, wtill well worth taking, has excellent range, and will worry him re the monolith, although in reality you are not much of a threat.
Loads and Loads of sisters. your flagelents I would be wary of, not cos they can not be effective against crons, they can be very effective, but accordingly he will target them, you may find they rapidly get peppered.

this is a case for ammassd bolter fire, with divine guidance where possible, eviscerators should be peppered over your VSS as you have done.

Try and avoid close combat, even with celestians this is risky, your T and S make you a much easier target for him than he is for you.

Dont get distracted. particularly in the second half of the game, focus on phasing him out and you should get there

Well, I changed my list up (took out the priest and the arcos [425 points!], added another squad of sisters and an Exorcist) and it paid off bigtime.

We were playing search and destroy, and for some reason he hadn't given his lord the VOD, which threw me off (I had anticipated him teleporting in on the first turn and deployed accordingly).

Turn one, exorcist fires 5 missiles at his Heavy Destroyer, completely failing to wound.
Turn two, six missles at the Heavy Destroyer, obliterating it.
Turn three, six missiles at a squad of Wraiths, obliterating them.
Turn four, six missiles at a squad of Pariahs, killing one.
Turn five and turn six spent trying to nuke his Monolith, the result of which was one weapon destroyed. Yay - one less unit affected by the stupid arc flux hibbety-jibbety. Bah.

Overall, the Exorcist more than paid for itself - I probably wouldn't have won without it. Thanks for the advice - I'm sold on it.

*edited for grammar*