Strategy

The Putricide fight is composed of 3 phases. The first two phases are pretty similar and can be considered the same.
Phase 1 goes from 100% to 80% (+ time to cast his Tear Gas in order to stun the raid at the transition)
Phase 2 goes from 80% to 35% (not exactly sure yet, might be 33%) (+ time to cast his Tear Gas in order to stun the raid at the transition).
Phase 3 goes from 33% to 0%.

Phase 1 is for you to "discover" the fight. You'll get some slime puddles to eat up with the abomination, an Ooze and if you're a little slow a Gas Cloud.
Phase 2 is the core of the fight where you get all his abilities.
Phase 3 is a DPS race with a big bad ugly boss.

The Abomiation :

The Abomination is friendly. It is actually a raid membre who has to go and drink a potion off the table (click on the table, and after a few seconds you'll transform). The abomination has 3 abilities : N° 1 is eating up slime puddles. This charges the Abomination's energy bar and allows you to keep a "clean" room. Without it slime puddles just flood the room and cause you to wipe. It is the NUMBER ONE priority for the player using the abomination. N°2 is a slowing ability which works on the Ooze and Cloud. This ability needs energy to be used. N°3 is a strong melee attack that debuffs the target increasing melee damage taken. It stacks a few times. This ability is a "if you have time" ability.

The Fight :

During the first two phases, you'll have to handle these 5 things :

Slime Puddles :

These are dropped in pairs by Putricide. They have to be eaten by the Abomination as fast as possible.

Volatile Ooze :

This is an add which appears on the right of the room. It's green. After is pops, it starts to cast its Volatile Ooze Adhesive. This will make it target someone and root that person (the person can still heal and dps, but not move). The person that will be rooted is NOT always the one targeted. The Ooze just seems to target whoever has most aggro, which is useless as it doesn't follow aggro. The Ooze is FAST, and needs to be slowed down. It can be slowed as soon as it spawns, so the Abomination handler has about 3 secondes to slow it down (can be done from a distance). If the Ooze hits its target, it will cause an exploion doing massive damage split among people arround the rooted player. If you see this is going to happen, pack up on the player so he doesn't die. The explosion also bumps everyone, and the Ooze starts to cast another Volatile Ooze Adhesive on another player. A 2nd explosion should wipe the raid as usually people aren't back to full HP in time (and half the raid is too far away due to the bump).

25 Man difference : It is almost impossible not to have the Ooze hit the 1st target with current DPS gear. Be ready to pack up.

Gas Cloud :

The gas cloud looks more like an Ooze. It is orange. After it pops, it casts Gaseous Bloat and links itself to a player it will follow. You'll need to kitte it and the Abomination need to slow it down like the Ooze. It does MASSIVE (about 10k / 2sec) to the targeted player at first, so healers need to be ready. The damage goes down as debuffs initially put on the target decrease along time. It is said the cloud deals massive damage to the raid if it reaches the target. Some say it wipes the raid, others say it depends on how much stacks are left. This never happenned to us and should never happen.

The 1st pop is always an Ooze so you should start with the boss on the left. After the Ooze has a target, move the boss over to the right in order to be away from the cloud's spawning location. Repeat this until 35%.

Choking Gas Bomb :

These are vials Putricide puts down in pairs. They generate an orange cloud around them. This deals AE dammage of about 5k / sec so you have to move away. After a few secondes (10?), the explode and do massive AE dammage (20k?). You want to stand away from them.

Malleable Goo :

Putricide throws bouncing goo at someone. People in the path can be hit. It you are hit, casting and attack speed are increased by 200% for 15 secondes. It also deals massive damage to the player. You become useless. Melee are not targeted and usually are missed even if they are in the way (as long as they stay real close to Putricide). Casters need to stay away in order to have time to move. This is really a danger for healers.

Throughout P1 and P2, just go from side to side DPSing down the Ooze and Cloud, eating up slime with your abomination. It's that "simple". After a couple of tries, you should be ok with this part of the fight.

There isn't a lot of raid damage if people are careful and don't stay in slime pools, get hit by Malleable Goo or by Oozes and Clouds. The only big damage is from when someone is hit by an Ooze.
Healers need to pay attention as damage comes in spikes (explosion, Gas Cloud's first ticks, Malleable Goo).

A simple Ooze (and Cloud) strategy is to put your casters at max range from the spawn spot so they can DPS as soon as possible. Melee wants to stay a little further away in case they are targeted and rush in if not.
As a mage, I found out Iceblok make the Ooze change target so I can be used in case you are targeted and will be it. Just stay in the Iceblok until it is dead or far away. It should work with Vanish, Bubble, etc. but I don't have confirmation.

At the end of P2, slow down on DPS. You want to have no Ooze or Cloud left when he'll transition. Make him transition when one has just died. Having no slime puddle also helps a lot.

Phase 3 :

Here, there are no more Ooze and Clouds (yay!). Putricide goes to his table and transforms into a monster. He will STILL drop Slime Puddles and use Choking Gas Bomb and Malleable Goo. You still need to move and be aware. After the transition, the Abomination disapears and the player comes back as his normal character. We put a tank in the Abomination as only one is required for P1 and P2, but a second one helps a lot for P3.

As said before, P3 is a DPS rush as you don't have an Abomination to eat up Slime Puddles so they will flood the whole room.
The boss also puts a stacking debuff on the tank. This debuff deals increasing raid damage as it stacks. 6 stacks will OS most people in the raid. This is where the 2nd (and 3rd) tank(s) come(s) in.
Your tanks must taunt off each other repeatedly. This keeps the number of debuffs on each tank close and makes the healing easier on the raid for a longer time.
Just find out what works best for you. You have 8 tries left right? ;)

Basicly, just burn him down (pop Bloodlust or Heroism here) before your raids wipes or you run out of space if puddles were badly handled in P2 (if you reach P3, this usually isn't a problem, the tank debuffs are).

One last thing : if a tank dies, the boss heals himself. And the more stacks, the more heals on the boss. Your tanks shouldn't die or it'll make it much harder.

25 man update

You must now have 3 tanks as the buff to the raid damage makes it almost impossible to kill him before it is unhealable. 4 stacks on both tanks will essentially wipe your raid.