1. Watcher Irideus at the Aquatic Intake:
Interrupt the Earth Shield ability cast of the Primalist Geomancer, also interrupt the Demoralizing Shout of Refti Defender.
Beware of his bleed effects and spear flurry because this will make the tank take heavy damage. Do not pull the primalist together with trash mobs because they have the Tailwind aura. Avoid Irideus's ground puddles which damage you over time, also interrupt his purifying blast from the Nullification Devices.
For Mythic difficulty, whenever you remove Ablative Barrier effect, Irideus will cast Reactive Spark which will react with the ground puddles to wipe your group.
2. Gulping Goliath at Goliath's Lair:
Interrupt elemental focus from the shocktrooper, the dazzle from the dragonfly, and also make sure you have infused mushroom buff or else the swoglets toxin will instantly kill you when it reaches 10 stacks. Kill the swoglets as soon as possible.
When Gulping Goliath gives the Hangry Enrage effect, you can dispel it. However, on Mythic difficulty, it cannot be dispelled and each stack of the effect will give you 3 debuffs of Gulp Swog Toxin. Sidestep his Belly Slam, you can see it from the ground animation projections. Healers should cast group heals whenever Gulping Goliath is casting Overpowering Croak and focus single target heal on a team member that gets Gulped effect.
You may need to use your defensive cooldowns and healing cooldowns when he casts Toxic Effluvia for area damage.
3. Khajin the Unyielding at Khajin's Gambit section:
Interrupt the Rumbling Earth of earthshaker because it will stun the whole group within 8 yards. Also interrupt the thunderstorm cast of galesinger.
The proto-dragons may get a buff called Binding Winds. Sidestep a frontal area damage ability Gusting Breath from the proto-dragons. You can also dispel their stuns. Use temporary immunity cooldowns or potions to survive the Hailstorm ability of Khajin the Unyielding, or run behind an Ice Boulder to survive.
For Mythic difficulty, Khajin will have another ability called Frost Cyclone, this needs to be avoided and kept away from the protective ice boulders. Healers should maintain a heal-over-time effect on the group because Polar Winds group debuff cannot be dispelled.
Anyone who gets targeted by Khajin's Frost Shock needs focused single target big heals and the Slowing debuff also needs to be dispelled.
4. Primal Tsunami at the Infusion Chamber:
Aqua Rager will begin casting Tidal Divergence to become 4 Aqualings, but this can be easily dispelled because it takes him 6 seconds to cast it. When you go to the end of the bridge, the water swirls stop and Sariya will finally be attackable, you can't interrupt her Inundate ability.
You must always interrupt Aqueous Barrier absorb shield, and avoid her Flash Flood area damage because it pushes back the whole group and deals group damage. Avoid the Infused Globule from Primal Tsunami at her phase 1 and phase 2 because it hits high damage and then triggers Waterlogged debuff.
In phase 2, you need to avoid the Crashing Tsunami, and kill the 2 primalist infusers to get back to phase 1. The infusers Infuse ability need to be interrupted or else it will empower the boss.
For the Mythic difficulty version, Primal Tsunami will also cast Rogue Waves which send damage waves to the group.
The Tank should always be within melee range of Primal Tsunami or else she will also cast Undertow, and use active mitigation when she casts Squall Buffet which will push the tank back and apply Focused Deluge debuff.
If the tank gets pushed back by accident, he should get back within melee distance as soon as possible.
Healers need to time their heals over time abilities to deal with Primal Tsunami's Tempest's Fury group damage, and dispel the Waterlogged debuff as soon as possible.