Ragnaros

** Must have 2 tanks and 2 heals. **

Spells:

Wrath of Ragnaros (melee) - used about every 25sec, those in range are sent flying up- and backwards while also wiping threat
Hammer of Ragnaros (??yd) - random raid member with a mana bar is targeted with those in proximity being knocked back
Lava splash (lava proximity) - AoE at random to those close to lava flow
Elemental fire - DoT (4800 over 8sec) inflicted to target with aggro
Magma blast (??yd) - ranged attack that inflicts 4000-6000dmg (used only when nobody is in melee range)
Melt weapons - weapon durability degrades quicker per hit
Summon sons of flame (see phase 2 in battle strategies)

Battle Strategies

Landing in lava (minimum 2 tanks, 2 healers, 3+ DPS)
Phase 1

MT and OT position themselves in a way so that they land in lava (not ground) after Wrath of Ragnaros

MT starts in melee, while OT is positioned few yards behind MT ready to take aggro immediately after Wrath of Ragnaros
Tanks must be comfortable moving through lava for this to work

mDPS should move out before every Wrath of Ragnaros so as not to take fall damage or risk dying in lava
rDPS and healers should spread out, back against wall, yet not risk being out of range at any point (including healers when Wrath of Ragnaros is done to tank)
Healers be ready to also heal tank that is in lava in case
Levitate may be useful to hover over lava and decrease travelling time (?)

Phase 2

Landing on ground (minimum 2 tanks, 2 healers, 3+ DPS)

Same as for above strategy, but healers will have to heal both tanks after Wrath of Ragnaros to prevent a death from fall damage
Slow fall, levitate, Noggenfogger elixir... may all be extremely useful in this case if used at the right time