Some general tips and tricks for Arms Warriors (and maybe other specs/classes) in M+ that I have figured out to optimize Arms in M+
Atal’Dazar
Rezan: Rezan uses a fear. In order to maximize uptime you can use Bladestorm in order to ignore the first fear, berserker rage to ignore the second, Bladestorm again for the third etc.
I suggest using Bladestorm first because its cooldown is lower than Berserker Rage when you play with Anger Management
Yazma: You can save up Warbreaker or even better Bladestorm (because Warbreaker is more important single target) to get rid of the player ghosts quickly.
Waycrest Manor
Heartsbane Triad: The first one of the Heartsbane Triad has a mind control and will use your cooldowns against your mates. You can try to make the timeframe in that you are mind-controlled easier for your mates by getting rid of abilities like Bladestorm, Die by the Sword, Stormbolt, Intimidating Shout.
Soulbound Goliath: The Soulbound Goliath will cast Soul Thorns on a random player. You can use Bladestorm in order to ignore the Thorns and maximize uptime/ free the ,thornsed" random player and hit the boss at the same time.
Gorak Tul: Gorak Tul will summon ads that stun players with a cast. You can use Bladestorm in order to ignore the cast and maximize uptime.
Shrine of the Storm
The water elementals in SotS cast an uninterruptable cast that throws the whole group in the air and pounds them into the ground. Arms Warriors can ignore the cast by using Bladestorm.
Lord Stormsong: Lord Stormsong uses a cast called Ancient Mindbender that places an Ancient Mindbender on top of a players head. You can use Bladestorm in order to ignore the Ancient Mindbender and also save your and your mates’ uptime.
Temple of Sethraliss
Merektha: You can save up Warbreaker/Bladestorm (better choice because Warbreaker is more useful single target) in order to get rid of the snake ads quickly.
The Underrot
Cragmaw the Infested: Bounding Stride can make Arms’ limited mobility more useful in this fight.
Sporecaller Zancha: Arms Warriors can use Charge (towards the Boss) as soon as Upheaval goes off. By doing that the Arms Warrior loses no HP by the Upheaval itself.
Siege of Boralus
Hadal Darkfathom: Use Heroic Leap to get behind the statue when Tidal Surge comes in.
Freehold
Council of Captains: Chase Captain Eudora with the Heroic Leap.
Trothak: Trothak casts a Bladestorm - you can use Die by the Sword in order to maximize uptime.
Harlan Sweete: At 30% all damage Harlan takes is increased by 100%. Try to get a Warbreaker in before the execute phase.
The Motherlode
Coin-Operated Crowd Pummeler: Try to get a Warbreaker in while the boss is affected by the Blazing Azerite debuff.
Tol Dagor
The Sand Queen: Use Bladestorm in order to get rid of Sand Traps (you are immune vs the stun effect) and Stinging Parasites.
Jes Howlis: At 70% Jes Howlis stuns all group members and opens the jails - you can use Bladestorm to maximize uptime.
Kings Rest
King Dazar: King Dazar uses a cast Quaking Leap. Shortly before he is done casting Warriors can use Heroic Leap to get away from the group. There he somehow is stuck in the air and the affected warrior loses significantly less HP. After being stuck in the air he runs back to the tank -> you can use Charge against him.
Also you can use Sweeping Strikes/ Bladestorm to damage him and his raptors.
Let me know if you got some more.