Basically it is the Setzer-cheese. If you already know about it and done it, than you do not have to read this guide, there is nothing else more to read here.

If you do not know what it is all about - stay tuned!

First of all, lets go through the units used:

We use 2x Rikku (i know a dealbreaker for many, but hey .. if beating the boss is your objective!) - if possible equip stuff that raises the possiblity to get your LB more frequently (idealy every round). I used overdrive (event) and aigaions Arm (trial), also mogs TM x2 (event) to push the LB-production of both my rikkus. Aside from that, try to gear for highest stats possible in HP, Def and SPR. also remember to get them resistant to petrify, confuse and paralyze because otherwise you WILL run into a problem.

Then we take 2/3 Setzers (depending how many you have and dependent on your friend unit) and equip them with a repeatable element and ideally with DW (does actually not matter if you have a source of dual wield or not on 2 out of 3 setzers), I personally used 3 Flametounges - they are cheap and have fire-element to them but you can also opt for lightning or Ice if you so desire. 2 of your setzers will be chaining prismatic flash and the third setzer will finish with Double Dice (if you do not have any DW-Tms .... just put second knife on our double-Dice finisher if possible so you can practically double the damage-output of your finished chain, but, with enough patience, it should also work without any DW at all) - the esper for your Finisher should be either diablos or Ifrit, because both have a corresponding killer. Also try to buy or craft plant and Demon killers and put them on your finisher. At last you can equip sun barette for another corresponding killer to your finisher-Setzer. Also remember how to finish correctly with a setzer ... he hits very fast with only a small window between activation and the actual hit. Building a nice chain by practising on the dummy, will actually help you a lot. Your setzers should be made immune to confusion, because otherwise they could rum amok among your group, causing a wipe.

Last unit is either a friend unit or an own unit that takes the function of a mana-backup: You should take a Mana-battery with you -> units like Ling, Tiliith, Ilias etc. and put them on Odin if they lack a dispel-ability for fingersnap. You only need to dispel the big one, as he can oneshot a re-raised unit with one ST-Attack, so be mindful of that after 50%-HP. The Best unit to be used here is a fully enhanced Ace that has a little bit of survivability. We do not really need his damage, so he can be built to just "support" by his imperils, his mana-ability and fingersnap from odin. It is best to also prepare this unit to resist petrify, paralyse and confusion

I did not waste any time on blinding the adds or dispelling them, as with a nice chain and a good hit from setzer I was able to do about 30-50% hp damage to the Adds and also do damage to the boss in the same turn, which makes this fight a lot faster than one could expect (it took me around 8 minutes in my best try, and around 40 minutes when the big marlboro got revived 4 times).

so in the end ... success mostly comes down to the first turn -> you NEED to get a LB with rikku by doing a chain with your Setzers. I had only one try where i did not initially get enough LB-crystals to get one of them at least a limit burst.

The other Rikku is then free to do what she wants, she can either revive other units (at the 50% treshhold one of your units will probably die) or do the most reasonable thing once the LB is casted which is DEFEND.

That strat worked out pretty well for me and those units are at least somewhat accessible.

EDIT.: It just got brought to me, that it is also doable with 2x chizuru setzer or 2x amelia Setzer. So basically if you can build a AOE-chain and have a setzer 2x Rikku, you should be good to go.

EDIT2.: It has been brought to my attention, that a lot of youtubers already sucessfully did that strat, so if you need a representation, you can look it up there.

EDIT3.: http://imgur.com/a/t6wuk