To reach Fankriss the raid will have to fight through the "Bug Tunnel," often called the "AQ40 Suppression Room" due to its similarity to Broodlord Lashlayer's room. The tunnel is filled with Vekniss Soldier Packs. Each pack contains a Vekniss Soldier and many many Vekniss Drones. Both the soldiers and drones respawn extremely quickly; standing still and killing them is pointless as they will respawn nearly as fast as they are killed. Instead, you must drag your way through the tunnels until you are tanking a large number of Vekniss bugs, then AoE them all down. Any players who die must run back and get summoned; it's very difficult to take the time to resurrect fallen players. After most of them are dead, you can resume running and dragging more bugs. It should be noted that, despite the similarities, the Bug Tunnel is much easier than the Suppression Room in Blackwing Lair.
At the end of the tunnel is a small alcove to the left called the "Safe Spot." You can run there to resurrect, summon, and rebuff before engaging with Fankriss. Players must be very careful not to wander too close to Fankriss as his aggro radius is huge and anyone more than a few feet beyond the "Safe Spot" will pull him.
Attacks and Abilities
Fankriss melees very light on maintanks - no harder than his brother Kurinaxx. A geared shaman and druid can keep up the MT's on Fankriss easily.
Mortal Wound — Stackable debuff on the MT that reduces healing by 10%. This is a cleave attack so it can hit multiple people in front of him. Rotate him between two MTs to let this wear off. (Very similar in shape, design, and abilities to Kurinnaxx.)
There are 3 "bug tunnels" around the room. Starting shortly after the pull then once every minute or so, each tunnel will spawn 4 Vekniss Hatchlings. With each spawn, one player will be ported and rooted in one of the small alcoves around the room. These bugs hit for 300 on tanks, 800-900 on cloth, and can be snared or feared. They will need to be offtanked for most of the fight.
At random times during the fight, one to three yellow-colored level 63 Elite worms called Spawn of Fankriss will spawn in a random location. They hit for around 2000 on cloth. They will also enrage after 20 seconds if they are not killed. Enraged worms deal 10-20k per hit, one-shotting anybody they're on. They are by far the most important part of the fight, as they must be killed immediately. They can be stunned, so all is not lost if they enrage just before they die.
If for whatever reason Vekniss Hatchlings get loose, they will need to be DPSed down or kited. If it's relatively early in the fight they should be DPSed quickly, but later on in the fight you are better off kiting them with frost traps, fears, anything you can. They cannot be frost novaed, or snared with any frost bolts.
As of patch 2.0.1 about 8 Vekniss Drones are spread out in the room and will all attack when Fankriss is engaged. Have the tanks pull them together and the DPS AoE them down.
Fankriss is very easy to tank. Your 2 weakest tanks, plus 2 decent healers, can keep him under control for the entire encounter.
By far the most important part of the fight is killing the Spawn of Fankriss wherever they occur. If they are not under good control, they can wipe your entire raid.
The snakes seem to spawn in groups of 3, one after another. DPS must be very fast on the first snake so that you can get on the second and third snakes quickly. The idea that that a snake will spawn every % of life Fankriss loses after the first one spawns has been proved false, but they do tend to come in groups of 3.
If a snake goes Enraged it will one-shot anyone it touches. Stunlock it if you can, otherwise kite it until it dies.
DPS on Fankriss will need to push it as fast as they can. (but save those DPS cooldowns for snakes!) Time is against you in this fight.
Tank(s) assigned to intercept Snakes should remain in berserker stance while DPS'ing Fankriss. This way they can more easily use Intercept. Hunters can help with distracting shot too. The worms CANNOT be allowed to kill healers. It is recommended to assign 2 healers to snake tanks, snakes deal heavy melee damage when not stunned.
It is rare but possible that Fankriss teleports one of your Hatchling tanks. When this happens, some hatchlings will probably get out of control. They will need to be DPSed down.
It is also possible that the Spawn of Fankriss spawns in the suppression room. This can pull extra aggro from Vekniss packs. The vekniss bugs will need to be DPSed after the snakes are dead. Suggestion is at the start, one of the hatchling Tanks just AoE taunts and picks up these mobs from the start of the suppression room avoiding any issue with a Spawn of Fankriss making the add.
Similar to how Nefarian phase 1 can be tanked with two sides or with a throne strategy, there are two ways to tank Fankriss hatchlings:
One tank in each bug tunnel (3 total) using demoralizing shout and thunderclap for short-ranged group aggro. Healers assigned to each tank will stand on top of their tanks, so that any healing aggro can be tanked easily. (After the 2.0 patch, this method of Nefarian and Fankriss is much more difficult to execute, due to changing game mechanics.)
The whole raid in a pile, with a single tank Battle Shouting to get aggro.
If your guild has a paladin with [Blessing of Sanctuary] they should cast that on the tanks over [Blessing of Kings]. BoS reduces the damage taken by tanks by a fixed amount per hit. This helps out much with healing the hatchling tanks. Horde side, Stoneskin totem can be of some use here as well.
Hatchlings deal 250-300 damage to a tier 2 tank, therefore each spawn of 4 hatchlings will deal 1k damage per hit to whoever's tanking them. As more hatchlings pile up, tanks will quickly start taking enormous amounts of damage. There are two ways to handle this:
Periodically call AoEs on the hatchlings. This is recommended with the single-tank strat since all the hatchlings are in one place. AoEs should preferably happen right after 3 snakes have been killed, so you don't risk a snake spawn while you are AoEing.
DPS down Fankriss fast enough that hatchling tanks don't get overwhelmed. This is recommended with the three-tank strat since it is difficult to bring snakes together for AoE. After Fankriss dies you can bring all the hatchlings together for AoEs.
An alternative way which works just as well for grouping up all the hatchlings is to have mages continuously spamming rank 1/2 arcane explosion over Fankriss and keep judgement of wisdom up on Fankriss. The Aoe on Fankriss will replenish mana quickly and the low level spam shouldn't pull aggro off the tank. Just spam continuously throughout the fight only holding dps once a worm is up. This keeps hatchlings to a minimum on said tank which allows for slower fights with easier healing.
Hunters should not attempt to Feign Death and wait in the safe spot before the pull if a Fankriss Attempt wipes. You will eventually aggro the entire tunnel, which will run to the front of the instance and destroy anyone who has zoned in.
However, wipe recovery IS possible if a DI, a soulstone or a shaman dies in one of the tunnels the hatchlings spawn from. The easiest is obviously the one closest to the hallway you entered from. If a wipe looks imminent, get the raid to run right up the tunnel before any DI's etc, people close to boss release and get summoned etc...
Although, in most cases, it's better just to reclear the tunnel. Overall a reclear of the tunnel will take less time then it would to rez 5-10 people and summon 30 more, then rebuff everyone. Most warlocks would not like this, as they only have a finite number of Soul Shards to use for Summoning.