The Panther Boss, also quite stealthy

Arlokk Abilities:

Stealth: Arlokk will stealth 3 times during the fight, same as vanish.

Mark: Arlokk will place a mark upon a player and all panthers will attack that player until it fades. This lasts 2 minutes.

Summon: Panthers will be summoned on both sides of the chamber in the 2 semi-caged in area's.

Fight:

When the fight starts some panthers and Arlokk will appear to fight the raid. Have 2 tanks assigned to panther tanking. One on each caged area. The panthers dont deal much damage so you can keep one healer on them. Have your DPS do as much damage as they can as fast a possible as she will dissapear/re-appear 3 times max and if after the 3rd re-appear you cant kill her fast enough you will be overwhelmed.

When Arlokk is hurt enough she will stealth and the raid will have to wait until she re-appears. Each time she appears everyone except the 2 tanks for the panthers should focus DPS on her until she vanishes again.

When Arlokk re-appears for the third time time is of the essence as the panthers will start to spawn extremely fast and can overwhelm the raid quickly.

One nice trick is to have the panther adds tanks use green whelp armor to put the panthers to sleep thus negating alot of damage.