We did it last night (2nd night of solid attempts) using the general strategy posted here. World of Logs report is linked below. Our raid comp was:
2 Tanks (druid and DK)That comp is far from optimal, it's just what we had. Our enh shaman DC'd for the night so one DK had to get improved icy talons which dropped his dps for that fight. Also having 3 boomkins was far from optimal DPS.
6 healers (2x shaman, paladin, druid, disc priest, holy priest)
6 melee (2x DK, 2x rogue, retadin, warrior
11 ranged (3x warlock, 2x mage, spriest, 3x boomkin, elem sham)
The first key to this fight is the transitions and set ups to just get into phase 3. We first gave this a try weeks ago with no real plan, and bad positioning in phase 2 constantly wiped the raid with Static Disruption. We killed Runemaster first, and when he's at 10% we hold off and wait for an overload. Once that goes off, they are positioned together and everyone stacks in Steel's melee hitbox next to Stormcaller. We used 3 soakers (spriests are the best, otherwise warlocks) so they got out at range. Make sure they don't stand behind the Steelbreaker tank (for when he runs out), and make sure they don't stand too far out that they don't get healed.
Our phase 3 strategy was to use 2 soulstones or 2 battle rezzes (1 per tank) to give us 4 tank phases. The first night of attempts we had 3 tanks and 7 healers, and our dps was nowhere close to enough, while tank/raid healing didn't seem to be a problem. We figured that even with dropping a tank and a healer for 2 more dps, we still would need 4 tank phases. To kill him in 3 tank phases the raid needs 126k dps, and to do it in 4 the raid needs 108k dps.
With everyone stacking (melee at steel's back and ranged standing on the steel tank), keeping the raid and tank up was no problem. We never had tanks coming close to dying until the 3rd one. Both shamans just spammed chain heal on the tank, which would keep melee and ranged up. Judgement of light also covered about 30%-50% of the melee healing. I was the holy paladin and non-stop HL spam on the tank put out amazing AoE healing with Glyph of Holy Light. The glyph heal accounted for over 50% of my effective healing, which is huge considering how much damage i'm healing the tank for.
After the first night, we found out there were 2 things preventing us from sucess. First was that we didn't have enough DPS even if everyone survived. That's when we dropped a tank and healer and picked up 2 more dps (roughly a 10% raid dps increase). Second, we really struggled to keep the Static Charged soakers alive during the 3rd tank (and never made it with all of them into the 4th tank). After the 2nd tank dies, there will be 2 people at all times taking 9k-10k evey 3 seconds (after resistance) from the nature aura and Static Disruption will hit for12k when applied.
We saved all our big cooldowns for the transition into the 4th tank and then the duration of the 4th tank. Since we only had two tanks, our druid went first and didn't use any cooldowns (doesn't need them). The DK went 2nd and used IBF just before his taunt, and then AMS on the first Fusion Punch. Both of those are on short timers so they would be back up when he tanks in phase 4. It's also important that your tanks don't resurrect during high damage times. Have them watch for ticks of nature aoe dmg and res just after one. Also, rezzing a couple seconds after Fusion Punch goes out is helpful.
Once the 2nd tank died, we had 2 dedicated healers for the soakers (disc and holy priest). Still didn't use any raid cooldowns for the 3rd tank phase. Just before the taunt into the 4th tank, we popped bubble and divine sacrifice. When a second before that wore off the ret paladin popped his bubble and divine sacrifice. The DK was also using his own cooldowns, and he got pain supression. The 20 seconds of divine sacrifice were absolutely key to have in phase 4, otherwise our soakers would have died instantly. During the 4th tank, they took 14k-15k from Static Disruption when it was cast, and 9k-12k from High Voltage every 3 seconds.
We ended up with about 109k raid dps for all of phase 3, and killed him with 7 seconds to spare. Oh, one other thing, we always blew heroism as soon as the first tank got Overwhelming Power. On our kill, we decided to use heroism as soon after the 2nd tank rez (start of the 3rd tank phase). No reason not to do that, since one person dying is a wipe anyway and it gives heroism during the execute phase. It's also a huge healing boost when you need it the most.
World of Logs
Phase 3 Only
Keys to this fight:
1. Get a good transition/positioning going from phase 1->2 and from 2->3
2. Amazing raid dps (110k for 4 tank phases)
3. Keep the Static Disruption soakers alive during the 3rd and 4th tank phases.