The last of our "new to Cataclysm" instances, Throne of Tides is an instance on the easy side of things whose greatest threat once you learn the boss mechanics are actually the trash pulls in the hallways to the last two bosses. 4.0.6 and the nerf to initial damage from the Gilgoblin Hunters can't come soon enough for the tanks I know... Oh, and while I don't usually do trash tips: Mages, Tainted Sentries + Swell + Spellsteal is very much your friend.
Anyways, the first boss you will face in here is Lady Naz'jar and she has two phases she will swap between during this fight; an active phase and a shielded phase. During the active phase she will need to be tanked and has two main attacks you need to worry about: Shock Blast, an interruptible spell that absolutely should be because it will hit the Tank for ~150K - making short work of those in early gear, and Geyser, a water void zone that will appear under a random player and, on heroic, must be moved out of because it will hit for 120K+ and instagib anyone. This phase is largely down to keeping that that cast from going off and avoiding those zones, but you will also want to avoid the patches of Fungal Spores which is a traditional DoT void zone mechanic you can easily get away from or dispell the debuff off if you're hit by it.
Twice in the fight she will run to the middle of the room and cast Waterspout which will place her in a shield that reflects magic damage, deflects ranged attack, and throws away any melee that try to get to her. During this phase three adds will spawn, two Tempest Witch casters and one Honor Guard melee mob. The traditional means of dealing with these is to CC the two casters while the Tank picks up the Honor Guard and you burn him down first before taking out the other two one at a time. The main reason to CC the casters is that they Chain Lightning (interruptible), to keep you from concentrating melee on the other mobs but you can CC any of these mobs. If you want the achievement, the easiest way to get it is to leave the melee mob CC'd for last, lower him to just below 100K, and then have your Tank move him into a Geyser during the "active" phase. The casters quite simply don't kite as easily with all that silly "casting" they do. Also, during this phase on heroic Cyclones will spawn from the Waterspout and move outwards towards random players in intervals. You want to prioritize avoiding these because they will pick you up and keep doing damage as long as you're trapped in them while also keeping you stunned so you can't heal, DPS or Tank until they drop you at the outer wall. Getting carried away from your Healer or, worse, finding yourself having agro on a mob who keeps attacking you while you're in the Cyclone is a good way to end up dead.
After 1 minute, Lady Naz'jar will rejoin the fight regardless of whether or not you've killed the adds so be prepared to pick her up and return to the active phase.
After killing her, and watching a short cutscene, you'll move straight to Commander Ulthok. His primary mechanic is very simple and, as such, he should be a quick kill. Basically, Ulthok will periodically wind up and cast Dark Fissure - the tank should back off when he does this - to pound the floor in front of him and create a void zone. On heroic, these void zones will expand indefinitely so the key to winning this fight is all about controlling these void spawns. The best way for the Tank to do this to work him around the outer edge of the room, only moving him forward as he drops each Fissure to keep enough space for the melee to work. For the moment, you can also cheat the mechanic by taking Ulthok out through the doors of the room for extra space to work with.
Other than that, he will place Curse of Fatigue on random people to slow their attack and movement speed and hinder their ability to dodge the void zones. Take it off when possible. Periodically, he will pick up and "Squeeze" someone and you'll simply need to heal them through it. Finally, he periodically enrages and this can be taken off with classes that can remove the buff.
Get your kite path down and this is a brutally short and simple fight.
Next up, you have a choice between killing two remaining bosses or just one.
The optional boss is Erunak Stonespeaker & Mindbender Ghur'sha. This is pretty much a two phase fight. In the first phase you'll be fighting Erunak Stonespeaker until he reaches 50% health. During this phase, the boss will cast a forward arc flame breath called Magma Splash so keep him pointed away from the party/stay out of his frontal arc depending on your role. He will also cast Earth Shards at random players which is easy to dodge for ranged - there will be an earthquake style split out towards the person it's cast at - but melee will need to be quick moving to get out of the area because it will create a rapid storm of earth spikes in the area where the person was standing that will eat through your health pool in short order. The last two abilities he will use, Lava Bolt at a random player and Emberstorm on the Tank, should be interrupted and dispelled, respectively, as quickly as possible.
At 50% Mindbender Ghur'sha will jump off Erunak and the second phase will begin in which you will kill him. Complicating this, Mindbender will periodically jump onto other players and Enslave them, gaining access to their abilities and giving them enhanced health as well. You'll need to burn them down to 50% as well to get him to jump off but, be careful with DoT usage because they can persist on the player outside this hold. Other than that, the primary source of damage to the party will be Unrelenting Agony, a channeled energy AoE on all players I'm told can be LoS'ed with the pillars but haven't had a chance to test myself.
The rest of his mechanics are more annoying than necessarily dangerous. Mind Fog creates a large green gas cloud in 10 yards proximity to Mindbender. This does mild DoT damage but, more importantly, Silences and Pacifies anyone in it preventing them from casting or doing damage. It's a good idea for healers and ranged to maintain distance to avoid this. Finally. he will periodically cast Absorb Magic - a self shield that heals him for 3X the amount of damage he would have taken from any spells. Wait 5 seconds for this to fade or spellsteal/purge it to remove it from play.
The last fight here is a three phase battle to assist Neptulon in freeing himself from Ozumat the giant "brother" squid of the Mindbender. Just so you're comfortable with his position, when you enter this room look up and to the right side of the dome. That's where Ozumat will make his appearance in phase 3.
In the first phase multiple adds will spawn and run in to try and kill Neptulon. It's the Tank's job to pick these up to both keep them off the boss and enable the DPS to burn them down. The first adds you'll see will be waves of non-elite Deep Murloc Invader's that are easy to burn down by DPS with AoE and a low priority to be tanked. Next up, you will see either an Unyielding Behemoth or one of three Vicious Mindlashers next as these mobs will slowly spawn into the room. The Unyielding Behemoth is a melee mob and must be Tanked or it will eat other classes whole in short order. It will also periodically rise up into the air and start pounding the ground to do an AoE, you should get out of this and avoid the frontal cone attack he will cast immediately upon ending the cast. The Mindlashers, on the other hand, don't hurt to be tanked but can be safely handled by DPS; especially those who can lock down their their Shadowbolt and Mana Burns with interrupts.
Once you kill the three Mindlashers, the second phase will start and three Faceless Sappers will spawn in around the room. The goal here is to focus fire these three down one at a time and end the phase as quickly as possible while the Tank picks up the Blight Beasts that will start spawning and kites them around the room and risks being overwhelmed if killing the Sappers takes too long. Complicating your efforts to do this, Ozumat will periodically spew black puddles at targets in the room. You should stay out of these and melee should simply move to the next Faceless Sapper if they can't find room to work anymore at the one they're on while leaving Ranged to finish that one off. Heroism/Bloodlust/Timewarp can be used here if DPS is tight to help push this phase over as quick as possible.
When the last Sapper falls Neptulon will buff the party increasing health, mana, damage done, healing and size so you can reach Ozumat to attack him while Ozumat will flood the room with his Blight, dealing stacking damage the longer it takes you to kill him. So, your goal here is to fight off Ozumat before your healer runs out of mana and everyone dies. The Blight Beasts from the prior phase will remain in the room so you can choose to finish them off now fairly quickly or simply just have all the DPS go to Ozumat and ignore them. If you haven't used your haste cooldown yet, once everyone's on Ozumat is the time to do so. Note that health regeneration tools like Frenzied Regeneration are currently immensely powerful here, especially as the Blight stacks start to build on the party, so it's a good idea to break them out to see to it you outlast the Boss.
Apply sufficient DPS and good heals, he will fall and you'll be done another run...