The pre steps mentioned are steps that can be done solo or in a group. the rest of the raid will be completed by the battlegroup as those steps need more people to complete.
For more information look here. Vision of Sages
on ml1.5 u speak to lord krojer and choose who you want to fight you only need to kill one then speak to another npc mob close by female mob she will talk to you and you click etc etc and you pass it but if you want a nice ring kill all the mobs lord krojer offers you then talk to the npc