This is going to cover the fight in very broad strokes. At present there are no YouTube guides available so this will have to suffice.

Tanks

• As usual this primal has a spicy frontal cleave. Offtanks should avoid standing near the front of the boss and DPS should avoid it at all costs.
• There is a vulnerability debuff that you will have to manage. If you're geared well enough and have a million cooldowns that you can rotate through (I'm looking at you, Paladins) it can be solo tanked. However, DF requires 2 tanks to queue in aaand lots of things can go wrong in the fight so having a second tank on hand isn't really a bad thing.
• In later phases of the fight Ravana will spam a hard hitting attack on the current main tank that will hit anyone standing behind the tank, even at range. You will need cooldowns for this part.

Healers

• There's going to be lots of damage on the tanks and even more on the party throughout the fight. There's not a lot of healing downtime.
• After Ravana spawns the butterfly adds and they're dealt with he will move to the middle of the platform, incapacitate then levitate the entire party. He then performs his Ultimate. This attack will wipe the party if the DPS failed the butterfly check. You will want to pre-SS or pre-HoT the entire party before the incapacitate > Ultimate occurs. Even then, if 3 or more swords are up when he performs his Ultimate, you're dead.
• Finally, when starts spamming his nuke on the main tank you will want to communicate and rotate cooldowns with them as needed. (think Akh Morn from T13)
• Heal all the things. Don't stand in the bad. Yell at your melee DPS for taking avoidable damage. Win the game.

DPS
Melee

• All damage from Ravana's cast time abilities can be avoided entirely by running away from him. Typically the edge of the arena furthest from him is the safest bet.
• Don't ever stand, run in front of or get near the front of Ravana. Unless you're a dragoon then by all means, go ahead.

Ranged

• Don't ever get hit by Ravana's cast time abilities. Just don't. Ever.

Melee/Ranged

• Our job, aside from not taking avoidable damage, is to pass the butterfly damage check. When Ravana summons the butterfly adds, don't get too distracted by the small blue ones. They need to die but it is infinitely more important to spot, mark and execute the larger red ones ASAP. When the red butterflies appear they begin a long cast. If the cast finishes before it dies a large sword is summoned at the butterfly's location. The swords are used by Ravana's Ultimate ability and will deal 2-3k damage each to the entire party plus another 4-6k blast at the end. The faster the red butterflies die, the fewer swords are summoned, the better chance you have of surviving his Ultimate and the happier you will make your healers.

Everyone
Occasionally Ravana will launch up into the air and perform one of two attack combos.

1. He will create 8 random lines across the arena floor, one for each member of the party. You will have a few seconds to get out of the lines then they will explode. Don't get hit by this. He immediately follows this up with an attack that covers the entire platform except for a small safe zone in the center of the arena.
2. He will create 2 lines that form an "X" on the platform. Same as before, you'll have a few seconds to get clear then they explode. Don't get hit by this. While the "X" is still present he immediately marks up 2 players with purple-ish marks. Marked players need to run to the nearest edge of the arena to give unmarked players as much room as possible to get clear of the impending blasts.

• As Ravana performs his Ultimate he will charge through the arena from one side to the other once for each sword successfully summoned by the red butterflies. Aside from doing massive damage, each pass Ravana marks destroys a section of the wall surrounding the arena. This is important to remember later in the fight if you survive his Ultimate.
• After his Ultimate, in the second half of the fight, he will follow up the two combos noted above by diving into the middle of the room and casting a large circular AOE that covers all but the outermost edge of the platform. Be prepared to move out quickly if you see the floor glowing a white-ish hue.
• Also after his Ultimate he gains another new ability. A cast time knockback…oh joy. You can tell the knockback is coming by a pulsing rainbow colored glow on the floor. Everyone will need to make sure they have their backs to a wall or risk getting knocked off the platform. Remember, Ravana broke sections of the wall with his Ultimate. Having someone mark these gaps is a good idea.
• Finally, Ravana will randomly mark 3 non-tanks with blue marks over their heads. These people will need to move to the edges of the arena and all other players need to move clear of them. Ravana will perform a single charge attack, similar to a dive-bomb (sans knockback), on each marked player.

If you can avoid these mechanics, you got yourself a win. If I've missed anything please speak up. I tried to be as complete as possible. Good luck and happy hunting!