What's causing the wipes?

Netches: This is a tankless battle. There's no point in taunting the boss, and it's utterly impractical to taunt the adds. The most dangerous thing about this fight is the boss's lightning AoE circle. People should be alert and dodge out of that ASAP. Ideally, tank should just be another AoE dps in this fight. If you're a stamina tank, equip dual-wield on your back bar and spam steel tornado, talons, and your fire breath. Ideally, you'll have a Templar healer who is constantly doing Repentance with the abundance of dead netchlings, which should keep the stamina users charged up, and ensure that the magicka users have enough stam to keep block-casting while doing their AoEs. Netchlings often go after the healer. Healer should not panic and run--it doesn't really avoid damage, and just makes it harder to AoE them down; instead, healer should run towards the DPS' AoEs.

Dwemer Army: Don't pull all at once. Pull a small batch, and the rest will come naturally as the initial pull dies off. Tank should taunt the centurions, and, if practical, the spheres. The group should take turns to make sure that some form of AoE mitigation ultimate is always up. Nightblades should use Veil of Blades, DKs should use Standard of Might, sorcs should use some form of Negate, and Templars should use some form of Nova. Healer should be constantly using Repentance to keep stamina users charged up and allow the DPS to keep block-casting their AoEs.

Engine Guardian: Harness Magicka (morph of the light armor skill Annulment) makes all the difference in this fight. It protects against ALL damage from the boss itself (though not damage from the adds), including its poisoned air. I always double-bar it, and it allows me to charge ahead during the poison phase without any form of healer support. Never, ever pull the levers. All that it does is abort the poison phase, and that is the best phase of the entire fight, esp. since Harness Magicka makes that phase trivially easy (we're always happy when the RNG gives us two poison phases in a row, since that's when we can do the best DPS on the boss). Three adds always spawn at the start of a lightning phase, and if the RNG gives you two lightning phases in a row, you'll have six. During this time, tank taunts the adds (when tanking, I prefer the ranged taunt so I can grab them as soon as they spawn) to draw their ranged fire away from the DPS/healer. Don't worry about hitting the boss until the adds are down. Once the adds are down, tank should try to do ranged DPS (snipe spam if stamina tank). Don't get sloppy--I've been in a number of runs where we wipe at the last moment because the boss is close to death and the DPS decide that they can ignore the adds; it's not worth the risk.