Karazhan Maiden of Virtue Strategy

Placement

Healers/Ranged - This fight is held in a circular room with many pillars, there are enough pillars for everyone to spread out and stand in between. Each player should stand right in front of the two pillars so they are in LoS to be dispelled.
Melee - There should only be a total of 3 melee hitting the Maiden at a time, this includes the MT, so two rogues at most. Everyone else should ranged and feral druids should just heal.
MT - Your MT tanks here where she stands.

The Encounter
Throughout the encounter she uses two primary moves which are holy fire, which needs to be dispelled IMMEDIATELY, and an entire raid repentance which lasts 10 seconds. The holy fire does about 4k initially and the dot ticks for around 1.2k, that is why it needs to be dispelled as soon as it hits. She also has a holy shock which is basically a chain lightning which increases damage as it jumps targets, this is why you can only have 3 melee in at a time. Your ranged also needs to make sure they don't get too close to the little circle platform she is tanked on as they will get hit by the shock. She also does a weak consecration which silences anyone that stands in it. Now she hits pretty hard, even on plate so you need to have 1 or 2 healers focused on healing the MT, 1 priest focused on dispelling, and 1 healer focused on spot healing (tree druid or pally).

Now there are a couple ways of dealing with her repentance, you can have your dispelling priest run in the consecration right as she is about to repentance and he can dispell a healer. Or you can load your MT with HoTs the entire fight. Either way works. The repentance does about 2k damage people can help the healing by bandaging after it as the tank will most likely need heals.

Once you get the healing rotations down and learn how to heal through the repentance this is a pretty easy fight, just rinse and repeat.

KEYNOTES

The holy fire needs to be dispelled IMMEDIATELY as it ticks pretty hard. If you fail to do so it can wipe the raid pretty quick.
Pets and Druid forms are now affected by the repentance so don't rely on them to save your tank, be safe and put HoTs on him and keep him topped off at all times.
If the healers are getting overwhelmed a bandage, healthstone, or pot can save your life and also the raid, it is a 10 man so 1 player loss is 10% contribution from the raid or often 20% of your DPS.
The tank takes A LOT of damage so load him up with HoTs before the repentance so there is at least some healing on him at all times. He needs to be topped off all the time. Also lifebloom is a great spell for after a repentance. Healing assignments are a huge plus.
There should NEVER be more then 3 melee in range, including the MT, if there is more the 3 melee in range people start to die from the holy shock.
If you have a shaman put him close to the priest taking the holy fires and have him drop grounding totem to absorb most of the holy fires.