Hey Surehoof,
I'll try to help out a bit, but since I don't know a whole lot about governing factors in your raid, I might say some stuff you know already, or just might not work for you because my assumptions aren't correct.
First, the decision to bring Nef down another 10-20% during Phase 2 is going to be variable on how your healing is doing. Typically, raid groups make the decision to crackle him during this phase because it shortens Phase 3, however if your healing is struggling very much and can't get this down, then you've got to make a decision between keeping at it until they learn to do so, or putting more strain on your add kiter in P3.
If you do decide to push another 10-20% during Phase 2, things that would help would be to hold DPS on Nef until the groups are topped off for the crackle. Hybrids can help with healing by either popping cooldowns (Tranquility, Divine Hymn, etc) or just by focusing on healing at critical moments. For platforms that are struggling with healing you can put a shaman of any spec and have him/her drop healing stream totem and healing rain. Since paladin aura mastery won't help against nature damage, hunters running nature resist can help platforms without shamans with their nature resist. Encourage your healers to mana dump if necessary since P2 healing will be very intense. Paladins should use their aura mastery in Phase 2 to help combat the shadowflame barrage damage or when people are just getting on the platform to reduce the fire damage from the magma.
In Phase 3, when everyone is stabilized it's a good idea to get DPS classes with mana CDs to use them (Hymn of Hope) if healers haven't asked for them already. It's also a good idea for non-healing druids to save their Innervates for healers - a thing that works well is to innervate early and innervate on CD on a designated healer that will be expected to go through a lot of mana.
In Phase 3, after having done both the center and the side positioning of Nef, I personally favor the center position. I would recommend changing your strategy a bit though from the 180 degrees every interval to constant rotation. That way, players are expecting the movement since it should be consistent (think Halion) and will know to keep moving. If you use this strat however, your Nef tank should be ready to run through his body and turn him 180 degrees if fire is in a bad spot. The raid, which is at Nef's side, should do the same if they have too much fire as well.
There are some merits to the side strat as well, I'll try to write them out a bit and hopefully it'll help you decide which one you prefer. The side strat is a LOT easier for the Nef tank because he/she just doesn't have to move, ever. I've found that the raid on Nef also has a lot more flexibility to move away from fire. However, the add tank is really cramped in this scenario in the sense that his kite path isn't as predictable as in the circular strat, and sometimes having to double back is dangerous.
Warriors are the best at add duty, followed by paladins. You might be tempted to perma-slow the adds, but this can be problematic sometimes if the adds are slowed and can't move out of a Shadowblaze in time. As you know, adds keep their energy and will continue to do much higher damage to your add tank if their energy gets reset while they are huge. I'm not sure exactly what you're doing in P3 so I can't go into more detail here. If your add tank is dying, one thing that will help is if he/she watches the energy bar of the adds. At 50 energy he/she should expect to be hit much harder and calling out for big heals on vent is a good way to let healers know to use quick heals until the adds fall over. In emergencies without tank personal cooldowns use Pain Suppression/Guardian Spirit/Paladin Devo Aura Mastery/Paladin Hand of Sac + personal Bubble to help reduce some of the damage.
Here is a video of instructional add kiting on Nef 10. it uses the center strat:
http://www.youtube.com/watch?v=L_Vt21OC3pE&feature=related
If you're having issues with crackles, plan cooldowns around problematic ones (i.e. Warrior Rallying Cry, Shaman Spirit Link Totem, Prot Pally Divine Guardian, Priest Divine Hymn). Call out crackles before they hit so healers can get everyone up.
Whew. Well, I hope I didn't say a bunch of stuff you knew already. Best of luck! :D
