Get a good tank and a few BLM's... We have a tank in our LS (Galka Garret!) who can hold so much hate its not even funny. His magic resistance is almost null (I had maybe 1 resistance a fight in all DD gear, no skill+)
Chat filters are important. Have EVERYONE filter out, so that the chat filter icon says ON (this seems to confuse people? I don't know... The circle has to say ON for them to be filtered OUT)
Special actions taken on/by party
special actions being taken on/by party
Special actions taken on/by alliance
Special actions being taken on/by alliance
And make "Special actions on/by you" unfiltered (Circle says OFF). With these chat filters, you will see
Chlevnik starts casting Meteor
ONLY when it is being cast on you; when its on anyone else, it will be filtered. This way you will always know who meteor is being cast on, and that person can run away from Chlevnik while everyone else runs toward him (This means that even if meteor hits that person because they were too close, it shouldn't hit anyone else) Make sure everyone has a /shout macro that they hit AS SOON AS THEY SEE meteor being cast on them - this lets everyone know to get the hell away from him.
Another small hint - he will use Meteor at 1% and it will drop him to extremely low health. We have had times where everyone screams "DEAD OMG WIN" and rushes to the box, and nothing happens... You must do at least SOME damage to him after his meteor, for god sakes just drop a Bio on him and go grab your loot.