SPOILER FILLED POST
Did you know that the Beatrix encounter is customizable?
Beatrix can only perform her class call-style spells when certain of her Lieutenants are alive.
Most players are fighting a combination of Infantry (Scarlet Phalanx), Artillery (Mortar Combat), Cavalry (Thundering Hooves), and Mage (Meteor) abilities. However, only two of these abilities are locked-in this week: the Infantry and Artillery abilities.
After defeating Balnazzar, when you talk to Fydriel, the Night Elf scout for the Argent Dawn, pay attention to the camps he says are empowered. These are the two guaranteed members of Beatrix’s encounter that week. However, players have the ability to choose two out of the four remaining camps they want to remove from Beatrix’s encounter. If you kill Cardinal Stiltz (Priest) and Bowmaster Puck (Archer) first, then you remove the Priest (Confession) and Archer (Scarlet Arrows) class calls from the Beatrix encounter. However, if you choose to kill Knight-Captain Fratley (Cavalry) and Arcanist Hilda (Mage) first instead, you will have removed the Cavalry (Thundering Hooves) and Mage (Meteor) mechanics from the fight.
Next week a new set of two mechanics will be guaranteed to appear in the encounter and your raid group can make a new choice as to what mechanics you remove.
The guaranteed mechanics are the same for all servers in all regions, so all raids face the same challenge, but may make different choices.
And yes, if you reset your instance before defeating Beatrix, you have the ability to make a different choice about which mechanics you disable.
Happy raiding!