Edited and updated based on Live experiences

Tanking: Two tanks: one for each of the active Golems.
When a Golem’s energy bar is almost depleted, after about 50-55 seconds, the tank should look to the other two to see which will become active next and be ready to pick it up. (This will be clear because the Golem that will activate next will have a beam to it from the back wall of the room, the colour of which signals which Golem it is.)
When a Power Generator (blue ground effect) is active the Golem in it must be moved out, and as much of the raid as possible should move into it.
When the Golems have their respective shields up (below 50% energy) tanks must stop attacking them as well.

Healing: Tank damage can be high at times.
The player with the Flamethrower debuff will need focused healing and probably a cooldown to survive, so be very alert to that.
If the raid is picking up stacks of Soaked in Poison for added DPS, there will be a high additional raid-healing load for the next 30 seconnds.

Positioning: The Golem with a shield on should not be hit, so they should be tanked apart from each other to prevent accidents.
When a Power Generator (blue ground effect) is active the Golem in it must be moved out, and as much of the raid as possible should move into it.
The rest of the time, the raid should remain spread out, to help reduce damage from the other Golems’ abilities.

Buffs: When a Power Generator (blue ground effect) is active the Golem in it must be moved out, and as much of the raid as possible should move into it.

Key Debuffs: Flamethrower – This player will be Magmatron’s Flamethrower target, and will need quick, heavy healing and maybe cooldowns to survive.

HP: 98,790,000 (32,209,000 on 10-man)

Enrage: Unknown

Bloodlust: When a large proportion of the raid are standing in a Power Generator and thus have buffed damage, or when the Golem is standing in a Chemical Cloud.
The ideal situation would see Toxitron and Arcanotron both active, to get both effects in play together.

The Omnitron Defense System is a group of four Dwarven Golems: Arcanotron, Electron, Magmatron and Toxitron. They share a HP pool, and only two are active at any one time.

When the fight begins, one Golem will spawn with 100 energy.
After 30 seconds, when this Golem is at 50 energy, he will put up a shield which causes Bad Things to happen if DPS doesn’t stop pretty much immediately, and a new Golem will spawn with 100 energy which DPS should switch to.
When the first Golem runs out of energy entirely and deactivates, after 60 seconds, the second Golem will be putting up his shield, and a new Golem will activate to replace the inactive one. DPS must therefore switch again to the newly-activated Golem.

Because the order of activation is not known in advance, the best way to talk tactics for this fight is to describe how to handle the abilities of each of the four Golems.

Arcanotron

Arcanotron’s main raid-damaging ability is Arcane Annihilator, which deals 50,000 Arcane damage to a random target. This needs dedicated interrupts as long as Arcanotron is active. A Shaman should be one of the interrupters so that they can also Purge the stacks of Converted Power.

He will also place a Power Generator, a blue ground effect, under his feet that grants 50% increased damage and increased mana regeneration to anyone standing in it, including the Golem himself. He should be moved out immediately, and the raid should make use of the buff this provides to increase their damage.

At 50 energy he will throw up Power Conversion on himself, which adds a stack of Converted Power to him every time he is damaged, increasing his damage and casting speed by 10% per stack. Only a few stacks are needed to make Arcane Annihilator a raid-wiper, so this cannot be allowed to stack.
Converted Power can be dispelled or spellstolen. Spellstealing this can be powerful but risky.

Electron

Electron will cast Electrical Discharge on a random raid member, which is a chain lightning ability that can jump to up to two additional players, increasing damage each jump. The initial hit is 30,000 Nature damage.

He will also make one player a Lightning Conductor, which causes them to deal 25,000 Nature damage every 2 seconds to players near them.

Because of these abilities, the raid should spread out when Electron is active. Depending on your healers and the damage taken from other sources, greater use of the Power Generators might be possible if any exist. Healers should get priority on these though, because it is a long fight and mana will be strained. This is something an individual raid needs to decide on.

When Electron gets to 50 energy, he will put up an Unstable Shield. If he is hit with this up, he will deal 60,000 AoE Nature damage, so DPS must stop before the shield goes up, to avoid triggering the shield. Electron’s tank must also stop auto-attacking.

Magmatron

Magmatron’s Incineration Security Measure shoots jets of fire across the room, dealing 15,000 Fire damage per second for 4 seconds. These are unavoidable and must just be healed through.

He will also cast Acquiring Target on a random raid member. After channelling for 4 seconds, he will shoot his Flamethrower at the target, dealing 35,000 Fire damage per second for 4 seconds to them and anyone else in the path. This is blindingly obvious, because of the huge red beam between Magmatron and his Flamethrower target.
The person being targeted should stand still, and the raid should move away from the path of the Flamethrower (the exception being if the raid is in a Power Generator. If this is the case, the target should move out instead).
Defensive cooldowns and focused healing will be needed to keep the person alive. NB: this can target a tank.

When Magmatron is at 50 energy, he will put up a Barrier, which absorbs 450,000 damage. However, if the barrier is broken, it causes a backdraft, which deals 75,000 Fire damage to the entire raid. As with the others, DPS must stop quickly so as not to trigger this.

Toxitron

Toxitron will channel Poison Protocol for 9 seconds, which spawns 3 Poison Bomb slime adds. These adds are untankable and will cast Fixate on and then follow random raid members. If they reach their target they explode for ~100,000 Nature damage and leave a poison patch behind. They can be slowed, stunned and rooted, and they should be kited and killed as top priority. Melee can attack them, as long as they are not one of those Fixated.

He will also throw a Chemical Bomb at a random player, which causes a Chemical Cloud to spawn at their location. Anyone within this Cloud takes 50% increased damage, including the Golems. So the tanks should move their Golems into the Cloud, and the raid should move out.

At 50 energy, Toxitron will put up a Poison-soaked Shell, which debuffs anyone hitting Toxitron with the stacking Soaked in Poison DoT, dealing 5,000 Nature damage per 2 seconds per stack.
There is a twist though: Soaked in Poison also makes your spells and abilities deal and extra 10,000 Nature damage per stack (via Expunge Poison). It may be beneficial for DPS to pick up a few stacks of Soaked in Poison, to do more DPS to the next Golem, but this will need to be checked with the healers, and should be limited to one or two stacks to begin with, and increased after consultation with the healers.