I used some ghetto version of Faxmonkey's spec, I don't really know what I was shooting for, but I couldn't respec because Ragnaros despawns for one day if you leave the instance for too long. Majordomo respawns after 24h or so and gm's won't spawn anything.
1) The most important thing to know is that if you are not in melee he will spam his Magma Blast spell which is instant cast and hits for 3-5k. Being next to him, getting hit, is not enough to avoid this. The game/spell won't recognize you as being in melee range unless you hit him every now and then. It is not just about proximity as previously thought. This means you have to target him by right-clicking so that you hit him from time to time during repositioning.
2)Nothing special other than that. Grasp the basic premise of the spec, control the spawns and you're golden.
I fucked up plently of times in this video as I was improvising and learning along the way, but that's mostly hilarous. Especially in the end where I almost die due to a lagspike, and I DID die in the end because I'm stupid and thought it was over!
Give it a shot, it's fun. I think the difficulty is around the level of Onyxia, maybe slightly easier due to the massive fire damage which gives sick amounts of mana from time to time.
Sadly I suck at compressing videos. The first version had razor-sharp quality and was 700mb or so, but WCM didn't like it. This one has Game Boy color quality, but at least you'll see what's going on.
Ironic that I post my first video here when I'm about to quit. Oh well, /wave..