One thing, DON'T over complicate this fight for you. I am the MT aka shield tank in our 10-man Feng kills.
* You as a shield tank will keep aggro on the boss all the time, your OT who is responsible for snatching the Fists, will taunt only off from you when the healers are struggling to keep you up. The shield you cast, will reset your stacks, as he won't build new ones up when he is channeling it. Or a good time is to take aggro when he has the fists already ready to use.
* You tank the boss so, that his side is to the railing, melee DPS are behind him, ranged and healers stand in bunch.
* Your raid starts to move to the shield tank when the shielded epicenter is coming, few seconds before it comes off from CD for the boss.
* When you have an unshielded Epicenter incoming let your raid know can you interrupt it or not. If you can't, it will give time for people to move to the opposite side of the platform, stack up and use few CD. Tanks should move from the center as well, since if your healers are on the other side you are out of range for them.
Lightning Fists is not a guaranteed ability he does, it might come from CD according to you boss mode, but he doesn't use it some times when it is available. So your raid has to be prepared for that. You can "keep" the Lightning Fists only for 20 sec, before it fades.
And as for our kill, none of the raid was well geared and our resto druid was in half green....
We have the shield tank eat LF whenever possible, and we manage to interrupt 75% of epicenters. We only pop barrier if we didn't get shroud. Consequently we have everyone stacked on the boss to make things easier. On the very rare occasion we miss LF for two epicenters in a row, we run out and heal the second.
I'm MT for the Feng encounter. I'm also the "shield" rune Tank and my problem is solely on phase 1 as all other phases are fine. I'm shielding on every other epicenter, and i'm supposed to get hit by lighting fists the other times. My Problem is 2 things:
1: I keep shield up full duration, taunt boss as he's running into raid and move so that he's facing phase 1's statue. When he casts Lighting fists (which usually his fists lands either directly in front of me or right the "F" on top of me) I don't get hit and raid has to take a full epicenter- this is like a 50/50 deal (happens half the time using this portion of the strategy)
2: I drop shield early taunt boss just before last tick of epicenter, as i'm about About parallel with him (if he's looking at raid- to his left) he'll casts lighting fist into center of the raid. After wards he's immediately on me and i continue to tank him while Facing phase 2's position. Then another 2 things can happen- 1: he doesn't cast Lighting fists again and raid takes an epicenter, or he does cast it again and it either misses/gets resisted or it hits and we continue as expected (again 50/50)
In the instances where he casts fists into the center of the raid, i've tried running over to where it will be to intentionally get get hit, however I never make it in time- even with using Death Advance (I'm a Death Knight btw). Also for the 2nd portion (where I tank him facing phase 2 position) the guild decided to use this strategy to combat the problem that occurs in option 1- we believed that my being so close to the fence/rail was the reasons the spell was "missing" me half the time.
We could not get this working in our raid despite multiple tries. So the way we do it is 3 heal (druid-me, resto shammy and hpally). The stun on the tank was causing a lot of damage so they just stand at the railing and everyone else is behind and the stun will never hit them because it goes behind them. So we shield first, defensive CDs and heals 2nd, shield 3rd, I pop tranq for 4th and we shield for 5th if we get it. Then we shield first draw flame, healing tide 2nd draw flame, shield 3rd draw flame then swap to 3rd phase. Shield 1st, tranq 2nd, shield 3rd, then boss is dead. This works out way better for us personally but may not be reliable for heroic but we aren't close to that yet.