Sorry, forgot about this thread. We couldn't beat it in 4 rounds, mainly due to too little knowledge going in. A couple more rounds and we would have had it. I do not believe this is do able by 6 blms though. Just to get you some quick info on it, when you go in there are 4 kings. (Nothing can be slept or lullabied, but can be hit with gravity) You choose 1, the other 3 vanish and 2 queens show up. The kings you can choose from are cups (whm), sword(pld), batton(blm), coins(rdm). You then always get a cups queen and batton queen, who are weaker versions of the kings.
The cups/whm will always bene at some point, queen and king can both do it. The queen did it to us at 1/10 and recovered over 5k hp. I hate to imagine if the king cups had done it. The queen cups casts a few holys and banishs, but no dmg output hardly. However, she spams cure 5 on the king if he is in range. Get a rdm or someone to pull it away from the king and she isn't an issue. Batton queen can't be silenced as far as we could tell and spams lots of tier 3 AoE and tier 4 single targets. Don't remember any ancient magic. The batton won't melee unless you run away from his spells. Then he absolutly wails on you with his staff. Batton loves to spams sleepga 2. So stay spread.
Now for the kings. Cups and Batton king function just like the queen versions, just more hp, hit harder. The sword king hits really hard and extremely accurate. He buffs himself and does a few cures as well. Coins king is the devil incarnate. He was our last one to try and it wasn't even close. He spams dispel, enfeebles, cures, buffs, nukes, all the while meleeing almost as hard as the pld king. Avoid the rdm king. He started the fight with chainspell on us and it was over quick.
If you want to do this I would say your best bet is whm king as the main dmg output is just from batton then. Downside is a 2nd benediction to tear through. Next easiest to kill is batton if you can go /nin to handle some of his nukes. If you don't have a lot with /nin, then sword might be a better choice.