/target Bone Spike
As soon as he bone spikes people (1 person in 10man, 3 people in 25man) hit this targeting macro and free your fellow raiders. Make sure that your raid isn't too spread out -- otherwise you'll end up running all over the place to free people.
Make use of Deterrence when Sir-Whirls-a-Lot gets into your neighborhood in his phase two. Just don't blow it before you need it!
For the adds, these are the targets we want to nuke. This macro will target them all appropriately and in appropriate prioritization. You specifically don't want to try and do physical damage to the Reanimated Fanatic which this macro specifically does not end up targeting.
/targetexact Cult Fanatic
/targetexact Cult Adherent
/targetexact Reanimated Adherent
Also, don't forget to occasionally toss a Vipersting on Lady Deathwhisper.