We developed our own strat for the most part, based on a couple things picked off this thread earlier on and from recording our own fights.

Setup our PT is using for repeated wins in a row:
2blm 2brd 2whm war drg/mnk (last one can be anything melee really)
Phase 1 - tank position him, move to your safe spot and go nuts. BLMs take a pause to take out the meteors around 35%
The safe spot is VERY close to where you spawn if the tank positions him to the right diamond shape on the ground. (from battle entrance PoV) This sets up a quick access route for BLM #2. Bards, don't forget to sing for the melee once in a while, especially if you have a MNK in the group.

Phase 2 - position him as before. 1 BLM head up the far stairs and take position on the mid-platform. Nail him down to 50%. 1 WHM, keep the wind DoT on him as it sticks pretty well. You'll notice the hp ticking away. 2nd BLM start out with Flare here, if the flame DoT hits, enjoy the results. Manage MP by keeping Stoneskin on your tank as much as possible, throw a Regen on anyone that takes AoE damage from Van Darnus.
At 50% BLM 1 begins taking out meteors while you keep hitting from the safe spot. When he goes Chariot x2 into Dynamo you should be safe. MNKs can drop Fist of Wind here at this point and keep it on, it allows them to run to the healers/archers at the safe spot and recover quickly without getting killed even after getting knocked back by Chariot. Dragoons can also do this, but it's a little more difficult without the extra speed. When in doubt, hold back with the healers if you are a dragoon, you are more valuable alive than dead for the big showdown. At this stage, the 2nd black mage might need to jump up and help take out meteors. Let BLM 1 make the call as to if he/she can handle it alone. If they can, you are rewarded with a much faster takedown. If not, no big deal.

5% - He'll speak about Oblivion, that's your cue. BLM + BRD goes up to a mid platform on either side (discuss this BEFORE the fight so it is instinctive ), sleep any golems along the way. Tank + melee go to the very top of the stairs (small green area) to the right of your tank (tank pov), which is the farther staircase for the mages . WHMs split up and meet at the very top of the stairs as well, each taking a different staircase. This allows any curing that might be needed along the way.

BLM + Bard throw up MP songs and start hitting meteors as they fall. BLM, this is your job for the rest of the fight at this point. (pretty simple eh?). the Archer/Bard can throw up Stoneskin/Protect for each pairing.
WHMs, one WHM keep your wind DoT on Darnus while buffing the 4 of you for Megaflare. Drop down to a lower staircase if a cure is needed. The second WHM, pop Cleric stance if you have not already, and go to town dropping 1/2 spell on each meteors. Depending on if you have to manage your MP, cover for buffs etc etc. This makes the BLM + BRDs have a much easier job, guaranteeing them precious MP for after Megaflare.
Tank + Melee, push out as much damage as you can to stop Darnus from regenerating.
At the top, you can keep track of the damage Megaflare will do. There are 3 circles, Each meteor that makes it through will cause a circle to fill up. 1 Circle is still easy to survive, 2 becomes a little tricky, and 3... well you don't want all 3 to be filled unless you like seeing the Damage Cap get reached by Megaflare. He'll denounce he is about to destroy you, when he does start running back down the stairs. Pray you didn't get 3 full circles! (following this method we don't miss a single meteor!)

Post Megaflare:
Run back to the bottom and take position. Have the tank grab Darnus and pull him back to his spot, recreating the safe-zone for the healers/archers. This part can be a little dicey at times because Darnus is doing a bit of wandering. Once the 6 of you are back on ground level, check your HP. Call for Benediction if you need it (as I said it can get dicey while repositioning him). Don't panic, as you're on the home stretch if you've got this far and are in good shape. Stay in your safe zone, knock out the meteors if you are a BLM. You'll see that last 5% drop off before you know it.

Congratulations, and good luck!