It's part of immortal flames quest line after the mini dungeon, and hte damned thing is near impossible. i've done it 20 times, all 50's, geared to the teeth, beat big ifrit, and don't beat this quest. @#%^ing ridiculousness.
It really isn't that hard once you have a tank who can keep hate and mages who can manage their enmity. I know it sounds like I'm dumbing it down, but it really isn't that hard. With the new patch today, it may be a whole new ball game though. I'm guessing now that people wont have to have 20 different skills from 10 different jobs it'll make it a bit easier. Here's a link that will hopefully give you an idea of how it was done. It may change after today's patch though. :( http://www.youtube.com/watch?v=V-1ZY3l9egU
Also, when my LS was farming dzamael, we'd take 3 archers instead of all melee. It's nice to be able to do damage the entire time instead of only half the time.