It is exceptionally difficult to sim accurately and make blanket statements regarding Mythic Keystones.
Each dungeon is different, what you should be prioritizing per dungeon is different.
Dungeon Slice and Hectic Add Cleave don't capture what you'll tend to be doing in most dungeons at a higher level,
so the method used to sim for the best gear setup in this instance is a 6 target 10 minute Patchwerk style sim with no Bloodlust to account for what you'll be doing most of the dungeon.
Run Trail in King's Rest and Workshop. Please note the cloak is at max resist to demonstrate end-of-expac gear.
https://www.raidbots.com/simbot/report/mJQkvvr7ybZbuGJEWr46VK
Priority
Lash of the Void x 2 > Twilight Devastation 3 > Ineffable Truth 1 x 2 >=
Twilight Devastation 1 > Expedient to fill out budget.
Item level does not matter for any piece except the Unguent Caress weapons you should aim for. However,
Twilight Devastation's damage does scale off of your max health pool, so keep that in mind.
If you're pushing high enough where damage intake is an issue,
you can consider swapping out any amount of Expedient for Avoidant,
which would effectively cap out your Avoidance while in Meta, or for Versatile.
You can also run under 40 corruption.
Trinkets
Merektha's Fang & Torment: Freehold, Shrine, Atal'dazar, and Waycrest
Vita & Torment: King's Rest, Workshop, Temple, MOTHERLODE!!!, Underrot
Special Dungeons
Merektha's Fang & Vita in Tol Dagor. Torment can pull things through walls, and potentially -
if you're not careful - end up breaking crucial CCs used on the mobs you'll try killing with cannons,
making the pulls harder.
Claw off of Maut & Vita can be used on high Siege of Boralus keys to attempt pushing
faster phases of Lockwood and Viq'goth to beat the timer.
Don't roll on this unless you know what you're doing.
Junkyard is a meme. Run Vita+Galecaller's and maximize Haste/Expedient for Zap.