To try and stimulate some discussion of trinity comp strategies, here are my notes from my initial Mythic +0 run of Tol Dagor. I use a blood dk/resto druid/BM Hunterx3 composition.
Much like, Siege or Boralus, this instance is completely fine until the final boss which is a complete pig to multibox. When I did this on normal during the leveling process, I thought to myself "Hey, this dungeon was really quite straightforward, I bet it'll be great on Mythic+!".Little was I aware that the extra mechanics on mythic turn it into a key-killer. Trash is pretty typical BfA stuff: difficult to chain pull due tothe abilities. In this instance in particular, I picked up a lot of fine detail that can be done on trash pulls to make it straightforward, too many to list here.
The Sand Queen: Easy. Follow the tank around, moving out of the sand traps when they spawn. Kill the adds that spawn, then immediately dispel the boss to get rid of the enrage effect when they die. Spread out the entire team in a clear space when upheaval happens then recombine immediately after. Try to kill the adds that spawn during the upheaval; that way, they don't buff the boss when they did. If the timing doesn't work out, you can soothe/dispel the buff off.
Jes Howlis: Easy to execute as intended. I position the ranged group in the corridor leading up to his "cage" area and tank him in the cage area. Interrupt the fear (it might be a wipe if screwed up and you lose control of the situation), then sidestep the entire ranged group when he casts flashing daggers. The little "sticky-out bit" at the join between the corridor and the boss's cage will happily break line of sight, so tuck the team behind it.
When he runs down the cage, charge after the boss, firing all the way. Tank picks up aggro on the adds and then they are all AoEed down together. By keeping up with the boss Motivating cry can be interrupted immediately. Bobby Howlis will likely cause mobility issues for the team on high keys, so the boss then needs to be tanked somewhere where it's very easy to hide from the daggers. Potentially, if one man gets left out in the open, an immunity (Turtle) might be incredibly useful here.
Knight Captain Valyri: I feel I need to see her on a good Tyrannical key to understand how hard she is. On +0, the strategy is easy. Park the ranged group in a corner and use the tank to reposition the barrels so that they do not cause them any trouble. If one gets triggered you don't like, reposition with a movement cooldown. Cinderflame seems scary, but fires in a completely random direction, so if the team is entirely stacked its actually very unlikely to point towards them. If not, then you get a very generous amount of time to pull them to a different corner.
Overseer Korgus: The Heroic/Mythic change to this fight, where moving too much causes a stun, really increases the difficulty of an already problematic fight. The eternal trinity comp problem: Moving out of bad stuff. The fact that the boss does unavoidable knockbacks makes this even worse. After experimentation, I have a pretty robust way of dealing with this: I shall try to describe as best I can, as it requires very precise positioning.If anyone needs me to draw a diagram, I can.
EDIT: Did so in a post below. Video: https://youtu.be/zc4n0CLGMU8
The big two problems are dodging the big cannons, and dodging the cross ignition. The cannon is easy: There is plenty of safe spots on the encounter area the cannons will never fire at. The cross ignition is harder.The most important thing to realize: The cross-ignition danger zones are NOT ina random direction. The boss will fire a cone directly in front of him, and then fill out a "hexagon" of cones around him. Crucially, that means that if the team is facing a direction perpendicular to the tank, positioned directly to the sides, that will ALWAYS be a safe spot. Of course, the knockback effect makes this a nightmare to achieve in the open space.
Here's the trick then: Before the pull, I set up in one of the two corners next to the entrance. Where the corner meets the stairs that goes up onto the outer platform, you can wedge a hunter in so that he won't get knocked back. Due to the symmetry, you can wedge one on each side. The idea is that I will tank the boss on a VERY precise spot such that the boss is pointing towards the corner of thew encounter area, so that the little nooks the DPS are hiding in are NEVER hit by the crossfire. One tiny mistake in the positioning of the boss, its a wipe. The other two team members are positioned on the high ground behind the two wedged in team members. When the knockback happens, these two may need to be repositioned manually. If executed perfectly, the fight is numerically straightforward, with very manageable incoming damage.
A note that somebody might find useful potentially that I discovered while experimenting: The boss can be tanked on the stairs leading up to the encounter area. This is a little dangerous, as if the tank gets knocked down the stairs the boss will despawn, so the tank should always be positioned so he gets knocked INTO the encounter area. This would allow you to position the team in space completely safe from the big cannons with a nice wall to stop knockbacks being so big a problem, but doesn't solve the cross ignition problem.
