Below is the details of the quest that Cadavahoof and I are currently working on for the legendary staff. The last part of contains the boss strat, and here is the link to the video from Sinwells downing of the boss. ET Video
This is exactly how to do the quest, from start to finish...
While fighting Lord Rhyolith you loot the Rhyolite Fragments from Rhyolite Fragments which randomly spawn around the edge of the area (note: possible link to the volcano spawns, but those are random as well). Gather three of these and create a Dull Rhyolite Focus, which is then used just before he uses Concussive Stomp. He has to stand on it almost directly so make sure you're pretty close before using it. Loot the Charged Rhyolite Focus afterwards.
While fighting Beth'tilac you loot the Obsidian-Flecked Chitin Fragments from Obsidian-Flecked Chitin, three of which spawn when a Cinderweb Drone is killed. Gather them and create a Dull Chitinous Focus, which is then used on top of the web just before she uses Smoldering Devastation. Go back up once it's safe and loot your Charged Chitinous Focus.
While fighting Shannox you loot the Emberstone Fragments from Emberstone Fragments, one of which spawns when a Crystal Prison Trap is destroyed. Gather three of them and create a Dull Emberstone Focus, which is then used just before he uses Hurl Spear. The spear has to hit the focus so make sure you're close. Once the fire has died down loot the Charged Emberstone Focus.
While fighting Alysrazor you loot the Pyreshell Fragments from Pyreshell Fragments, one of which spawns when a Voracious Hatchling egg hatches. Gather three and create a Dull Pyreshell Focus, which is then used just before she reaches Full Power (100 energy). It doesn't matter how close you are so just drop it where you're standing at around 90 energy and then loot your Charged Pyreshell Focus. Note that only two of the fragments spawn at a time, and that if you are usually flying around you will have to switch roles (or just have no-one flying at the start) to do this.
A very important note if you want to get Dragonwrath as soon as possible: do NOT kill any of these bosses. You can loot your charged focus then just wipe and move on to the next boss. Also note that if your raid is willing to let you do this, it only takes a few minutes to do the quests in between this one and Time Grows Short as there is no fighting or anything involved, it's just travelling and cutsecenes. To make this as quick as possible I'd advise setting your hearthstone to somewhere near Amber Ledge, like Williamson for Horde or "Charlie" Northtop for Alliance.
Once you have all four of the charged foci go to the portal near Beth'tilac and use them. After entering the portal you begin the encounter with Volcanus, which is a three phase fight.
Phase 1 - just interrupt and kill all of the Harbinger of Flame. You can burn mana and cooldowns to make this easier as phase two starts only when the player on the quest tries to loot the branch.
Phase 2 - Tormented Protector will need to be tanked at the entrance portal. He casts entangling roots which does damage, but only dispel them AFTER he does his stomp. If you dispel them beforehand you will get knocked back an enormous distance and die. Once he does his stomp dispel them as soon as possible. Small treants will spawn periodically and act identically do the transition phase adds on Ragnaros: they must be killed before they reach the treant. Ranged should deal with them. At the end of this phase he becomes friendly and casts Blessed Defender of Nordrassil on the player on the quest.
Phase 3 - Volcanus will fixate on the player on the quest (who is transformed into a huge tree of life) so tanking will not be an issue. Use ALL DPS cooldowns and burn him down quickly. There are a few spells to avoid, so as always do NOT stand in the fire. Healers have to compete with constant raid damage.