To try and stimulate some discussion of trinity comp strategies, here are my notes from my initial Mythic +0 run of Siege of Boralus. I use a blood dk/resto druid/BM Hunterx3 composition.
Very straightforward instance, other than the final boss as a very notable exception. Nothing too outrageous in the trash. There is a gauntlet where you have to dodge between cover twice in the instance that is usually the sort of thing that causes multiboxing troubles. Not so in this case: I found it far easier than similar previous mechanics, like in Iron Docks in WoD. There are a couple of nasty trash packs, but there isn't a single trash pack where CC doesn't make it very straightforward. Something to mention is that a melee comp is going to have massive troubles at multiple stages of this instance.
Chopper Redhook: One of those follow-the-tank-and-run-around-like-a-madman bosses. Nuke down the adds first then kite the boss into the cannon barrages. Feels very similar to the first boss of the motherlode: a bad barrage configuration will cause problems.I might try and experiment to see if the positioning can be manipulated. If the mechanics are well executed, and there's no reason why a multiboxer can't do so, its an easy fight.
Dread Captain Lockwood: I adjusted one of the BM hunters to spam concussive shot on cooldown and that completely sorted out the Evasive mechanic, stopping her jumping away. Had the entire party follow the tank and positioned the boss about 1/3 of the way into the encounter area. The reason for this is that, when the boss jumps to the boat and fire the cannons, the swirlies seem to target the three thirds of the combat area. By lingering on the border of two zones, I could dodge into the safe one when the cannons were first.
Hadal Darkfathom: During the "neutral phase", I have the party follow the tank and stay mobile moving around a circle about ten yards away from the central column to ensure there aren't any patches of frost damage close to the column. When break water is cast, I quickly scatter the party then quickly get them to refollow once done. When the wave comes in, as everybody is following its very straightforward to move the team into a position close to the column to avoid the wave.
Viq'Goth: ARGHHGH. 50 or so wipes it took me to get this guy down. Now, first off a reminder: I was woefully undergeared, and its entirely possible that its not that bad if you are actually equipped in something more than questing greens. However, on a high enough tyrannical key the experience is always going to be similar to being undergeared, so I'm glad I learnt to deal with it. The major problem here is the Call of the Deep ability which puts a large amount of blue swirlies in a wide area around a random player. Moving a random character out of large swirlies is, like, the most stereotypically difficult mechanics for multiboxers to deal with, e.g. Serpentrix last expansion. The damage from this ability is one of the hardest hitting things in any of the dungeons, according to the journal. It was one-shotting my guys when I ran it and, even with better gear, it will absolutely have to be dodged.
In addition, the magic debuff he places on the team is also difficult to manage. You want to stack up following the tank to dodge the swirlies, but this punishes that, as the knockback will cause chaos you likely won't recover from. The damage was too painful for me to just heal through,though I imagine better gear will completely turn this around.
Executing the fight "as intended" I managed to get through the first phase of three every other pull, with difficulty. I never managed to pull off a successful transition to phase two: precision jumping is another typical problem for multiboxers. Important note: the tentacle does not grab a character in the water if they are walking on the water, rather than swimming, so my plan to get from phase to phase was to use path of frost and a movement cooldown to get to the next platform before damage broke it.
In the end, I came up with the following incredibly long and cheesy strategy. This will potentially kill any timer dead in Mythic key runs,and certain affixes will also wreak havoc with it, so I'm not hugely satisfied,but it works. Here's the trick: If you stand on the little wooden bridges/platforms that lead from the main combat area towards the other two combat areas, swirlies from Call of the Deep NEVER land there. If you park the entire party there, that mechanics is neutered. The problem is then dealing with the tentacles, but here's another useful fact: Only a certain number of Demolishing Terrors spawn per phase. I didn't clock how many it was(6 or 7?), but once you kill a certain number of them, they stop spawning. The"tank" needs to be in melee range to stop these doing huge unavoidable AoE damage, which is incompatible with hiding on the platforms...but here's yet another situation where three BM Hunters saves the day. A pet can quite happily tank the tentacles for a short while. It'll die eventually,but there's two more pets in reserve and the pet can be cheaply revived.
So, putting this all together here's the strategy: We DON'T kill the boss using the cannons, as intended. At the start, nuke down the first Demolishing Terror, then immediately run onto the nearby platform to dodge the incoming swirlies. Once there, point everybody towards the tentacles and fire away. If they spawn right next door, you need to move around to avoid the frontal cone they do, taking care to quickly move back to safety afterwards. If they are a medium distance away, the pets quite happily tank while the team does damage to them. If they spawn all the way on the other side, we have a problem: We HAVE to kill the tentacles quickly enough so that two are not active simultaneously, or we will find it impossible to stop the lethal AoE. In this case, whilst the pets will happily run over and tank the distant tentacles, they won't do enough damage by themselves to kill this quickly enough. This is obviously not a problem if its the last tentacle. Otherwise,you may have to execute a dash across the combat area to the platform opposite to get into a position to damage the tentacle. This is note a problem if the run is timed: You want to do it immediately after the boss uses Call of the Deep. This can be difficult to tell because you don't see the ability if you are all hiding out on the platform, but as a guideline it seems to happen about 5-10 seconds after the Putrid Waters debuff is cast.
Speaking of which, my strategy with Putrid Waters is to manually control the most fragile character that gets hit with it and move them well away from the team into the combat area, dispelling them, then running back. Exhilaration, or any other personal healing cooldown, is very useful for managing this. With more healing, it might be viable to just sit and healing through the pain.
Once all the tentacles are dead, including the constricting tentacle holding the engineer, the hunters then nuke down the boss whilst standing in the safe zone. The boss has a lot of HP, but not so much so that it cannot be done. To make this slightly easier, you only need to get the boss down to 33%, at which point you can use the cannon to finish him in incredibly satisfying fashion. You have to manage the Putrid Waters debuff flawlessly the entire time: One screw up accidentally dispelling too early and the entire group is in the waters and dead.
I'll try and see if I can get a more conventional strategy worked out next week with my better gear making the fight more forgiving; I'm deathly afraid Blizzard will do something to nerf the "safe-zone"that makes this cheese-able. and very concerned for the timer on Mythic+ keys using the cheese strategy.
