For your 10-man raid makeup, you'll be aiming for two tanks. You'll want either two or three healers, with the rest of your raid being DPS characters. Whether you need two or three healers will depend on how sturdy your tanks are, as well as how awesome your raid healing is -- use your best judgement here. In 25-man, you'll need 2 off-tanks, and about twice as many healers. One of your off-tanks are going to have a special challenge in this fight, as he or she will have to pilot an abomination.
There are three basic phases to the Putricide fight. You get into the second phase when the Professor is at 80% health. The third phase begins at 35%. When the phases turn over, you'll get hit with Tear Gas, which will stun your entire raid while Putricide makes a dive for his chemical table.
As soon as the first phase starts, have your off-tank run directly for the table and immediately take over the Mutated Abomination. You do that by right clicking the table. The abomination is going to put out constant damage to the raid via Mutated Transformation, but the Abomination's ability to eat slime will make up for that detriment.
Throughout the fight, Putricide will lob ooze out to the raid. The Slime Puddles are bad news, doing significant damage to anyone who has the misfortune of standing in them. (So, don't stand in the ooze.) The Abomination has the ability to eat the slime puddles, which will both provide power to the Abomination and decrease the size of the puddles. If the puddles grow too large, then your raid won't have anywhere to safely stand. Every time the Mutated Abomination eats a slime, it'll pick up the Energy required to fuel Regurgitate Ooze, which will slow down the two adds that appear.
While in first two phases, Professor Putricide will summon two different types of adds. The raid warning will call out an Unstable Experiment when it's time for the add to appear. This happens about once every 40 seconds. The two types of adds are Volatile Ooze and Gas Cloud. The Oozes appear in the north portion of the room, where they leak from the ooze tank. Gas Clouds appear on the opposite side in the south. Both adds will choose a target and crawl towards it. They each have different special affects they place on their victim, and then an explosion they do if they reach that victim. If they're not killed before they explode, they will choose another target and start their attack routine all over again.
Volatile Oozes will spawn, focusing on a target and rooting that raid member in place. (The root effect is called Volatile Ooze Adhesive, and isn't just a clever name.) If the Volatile Ooze reaches the raid member, it will explode in a Ooze Eruption. The eruption will not only deal massive damage to anyone standing near it, but it will also knock everyone around the room. That includes knocking some folks into the Slime Puddles. So, it's important to burn Volatile Oozes down as soon as they appear, long before they manage to reach their target. If the Ooze does reach its target, however, the explosion is split evenly between everyone within range. If you're not getting the Ooze down in time, try and have the raid stack on the target instead, so as to evenly spread out the damage.
Gas Clouds will also focus on a single target, but they don't root like the Volatile Ooze. Instead, Gas Clouds put a 10-stack of Gaseous Bloat on its target. The Bloat will inflict damage on the target, while steadily dropping off on of its stacks every few seconds. If it reaches its target, the Gas Cloud will explode to deal damage to the entire raid. Obviously, it's best to burn down the Gas Cloud just as quickly as you burn down the Volatile ooze.
When Putricide hits 80%, he will drop that Tear Gas we talked about and enter Phase Two. He runs back to his desk and grows two tentacles. (I feel like I should make an anime joke here, but I'll skip it.) Putricide will start shooting Malleable Goo at random raid members. Anyone who stands in the area where the Malleable Goo lands will take huge damage, and receives a slowing debuff which will increase their casting and attack time by 200%. Goo will generally attack ranged targets first, but will target melee if there is no ranged target to affect. This is really the only completely new trick for the second phase, but everything from phase one will continue.
He'll also drop a Choking Gas bomb in between Malleable Goo attempts. They explode for truly massive damage, and should be avoided when you see them land. The tank should kite Putricide away from the area they land in, and melee should be careful not to stand in them.
When Putricide hits 35%, he'll hit your raid with Tear Gas, and then go mutate again. The third phases grants Professor Putricide Mutated Strength, which increases his damage and attack speed by 50%. When you attack Putricide, he'll put Mutated Plague on your tank. This plague inflict damage to everyone in your raid. At this point, your tanks will have to taunt-swap Putricide so that the Mutated Plague stacks never get too high that your healers can't handle the raid damage. You don't want to swap too often, however, because Putricide is healed every time the Mutated Plague drops off a tank. (For about 3% of his damage.) For 25 man, you'll need three tanks to make sure the plague doesn't get out of control, while you'll only need 2 for 10 man.
Phase three continues with the Gas Bombs and Malleable Goo, but no more Volatile Oozes or Gas Clouds will spawn. You won't have the abomination in the third phase, which is where you get the extra tank to handle swapping Putricide around. The Slime Puddles will still continue to grow, however, so you want to lean on the DPS in this third phase. Without the Mutated Abomination, the growing Slime Puddle will eventually overrun your raid.
In summary, here is the flow of the fight. Your main tank pulls Putricide, while one of your off tanks pilots an abomination. When adds appear, kill the adds. The abomination should be eating slime off the floor to give your raid safe places to stand, and placing its slowing effect on the adds. When you get to the second phase, don't stand where Malleable Goo is going to land. Continue to burn, steady like the beating drum. When the third phase happens, blow all your cooldowns, and burn him down as quickly as possible. If you stay too long in phase three, you'll have no place safe to stand. Good hunting!
Edit: Added information about Smoke Bombs, which I missed unintentionally. Thank you to the comments below for pointing this out.
Ready Check is here to provide you all the information and discussion you need to bring your raiding to the next level. Check us out weekly to learn the strategies, bosses, and encounters that make end-game raiding so much fun.