Arms has a decent rework in BfA Beta. The rotation is still similar to Legion, but less prone to RNG and a majority of the design issues from Legion are gone, more on that below.

A few Artifact traits have been carried over. Some keep their old name, or they were baked into another ability.

What's been removed

• Battle Cry
• Mastery: Colossal Might
• Focused Rage
• Mortal Combo
• Titanic Might
• Shockwave
• Opportunity Strikes
• Dauntless
• Trauma
• Corrupted Blood of Zakajz and Void Cleave are not coming with us to BfA.

What's been added

• Mastery: Deep Wounds replacing Mastery: Colossal Might.
• Skullsplitter in place of Sweeping Strikes.
• War Machine in place of Overpower.
• Sudden Death in place of Dauntless.
• Impending Victory in place of Shockwave.
• Massacre in place of Trauma
• Collateral Damage in place of Fervor of Battle (Fervor of Battle has moved).
• Warbreaker in place of Mortal Combo.
• Dreadnaught in place of Opportunity Strikes.

What's different

• Colossus Smash is now a 45s cooldown. Increasing all damage done on the target by 30% for 10s.
• Tactician now has a 1.4% per rage spent to reset the cooldown of Overpower.
• Overpower is now baseline. It now increases the damage of your next Mortal Strike by 20%, stacking up to 2 times (think of Shattered Defenses).
• Mortal Strike rage cost has been bumped up to 30 rage.
• Execute's rage cost has been bumped up to 20-40 rage.
• Bladestorm and Ravager both apply Deep Wounds when they deal damage.
• Sweeping Strikes is now a baseline cooldown with a larger range and less targets hit. It is on the GCD.
• Commanding Shout has been renamed to Rallying Cry. It's also on the GCD
• Rend is now a 12s duration, up from 8s.
• Avatar now generates 20 rage, and has swapped places with Fervor of Battle
• Cleave has been moved to a talent, in place of Titanic Might. Now applies Deep Wounds when it hits 3+ targets and it's rage cost has been bumped up to 20.
• Fervor of Battle now increases Whirlwind damage by 10%, and casts a free Slam on your primary target as well. This Slam is affected by Sweeping Strikes.
• Deadly Calm is now an active, moved in place of Focused Rage. It reduces the rage cost of your abilites by 100% for 6s (on the GCD).
• In for the Kill is the same, but now increases haste by 20% if the target is below 20% HP.
• Anger Management now also affects the cooldown of Colossus Smash.
• Executoner's Precision is now an Azerite trait.

Talents

There have been some significant changes to Arms talents.

15 - War Machine / Sudden Death / Skullsplitter

• War Machine is powerful if there's a lot of adds that die quickly. However, this isn't always the case of course.
• Sudden Death is the best choice for single target and cleave situations. I can even see it being used over War Machine in M+. Sudden Death has such a high PPM (2.5), and applies Deep Wounds AND Executioner's Precision if you have the Azerite trait. Sudden Death, like Ayala's Stone Heart, has so much damage loaded into it.
• Skullsplitter doesn't hit all that hard and the rage you gain from it isn't a whole lot either. It could have use when you need on-demand rage or burst on a target.

30 - Double Time / Impending Victory / Storm Bolt

• Double Time is an essential talent for Arms for rage generation.
• Impending Victory was added in place of Shockwave.
• Stormbolt might seem to be the obvious choice for M+. However, a lot of mobs in dungeons are immune to CC as I've seen in the Beta. And there are better AoE stuns on other specs.

45 - Massacre / Fervor of Battle / Rend

• Massacre allowing us to execute starting at 35% looks pretty powerful. It has great synergy with Executioner's Precision allowing you to get stacks earlier.
• Fervor of Battle is strong for AoE. Losing Trauma does hurt the build in single target and consistent AoE.
• Rend being a 12s duration is a nice QoL buff. You don't need to refresh it during the new Colossus Smash window and you spend less rage refreshing it.

60 - Second Wind / Bounding Stride / Defensive Stance

• No changes.

75 - Collateral Damage / Warbreaker / Cleave

• This entire row is all AoE/Cleave based.
• Collateral Damage only performs well on consistent 2 target cleave.
• Warbreaker of course still a really good AoE burst ability. Can't be parried, really good choice for single target to prevent that.
• Cleave steals the show. It can apply Deep Wounds to 3+ targets every 6s which can lead to Deep Wounds being 40%+ of your damage on AoE.

90 - In for the Kill / Avatar / Deadly Calm

• This row is all about cooldowns.
• In for the Kill is much weaker now because it doesn't nearly have the same amount of uptime as it does on live. Has great synergy with Anger Management and the haste steroid for the last 20% seems good.
• Avatar is basically the same. 20 rage every 1.5m is quite weak however.
• Deadly Calm feels really bad to press, but has potential for AoE when you really need to spam Whirlwind.

100 - Anger Management / Dreadnaught / Ravager

• This row has a lot of good choices.
• Anger Management is quite powerful, getting more Colossus Smash's off and more Bladestorm.
• Dreadnaught is really fun to play and offers a more frontloaded Mortal Strike gameplay style. Although a little weaker than Anger Management, it may have a place in BfA.
• Ravager remains the same but applies Deep Wounds as mentioned earlier. However, since Bladestorm hits very hard as well now, Ravager/Bladestorm choice might be dependent on the fight timers.

Where Legion fell short

BfA Arms Rotation is very similar to Legion Arms. The rework has addressed a few of the design issues Arms had in Legion. For example, the Colossus Smash window had such a high uptime meant it didn't work as a "window of opportunity". There wasn't any room to play around the debuff as procs were too frequent and random, so you couldn't prepare for it. This was also an issue combined with the massive amount of synergy between Colossus Smash, Precise Strikes and Shattered Defenses. When you experienced the lower end of RNG, your damage plummeted, because all your synergy and damage was loaded into this one big thing. There wasn't any "skill" in regards to the procs, just how lucky you are.

There was a slight rework in 7.1.5 which helped with Colossus Smash and the damage loaded into it. But that was mostly a band-aid to help the spec until a full expansion rework. Legion Arms is fine, but it could definitely use a refresh.

Where Battle for Azeroth picks up the slack

Battle for Azeroth improves on Legion's failures by reducing the reliance on Colossus Smash, and instead making it the spec's primary cooldown in place of Battle Cry. This allows the spec's baseline damage to improve considerably, and take emphasis off of random procced resets controlling damage output, making target swapping easier and reducing the emphasis on burst. Overpower replaces Colossus Smash's former place in the rotation, applying what is essentially the Shattered Defenses buff to Mortal Strike, and keeping Arms gameplay in Battle for Azeroth more forgiving, but overall very similar to that of Legion.

Overview

Shattered Defenses was moved into Overpower, increases Mortal Strike damage, free to cast and resets through Tactician. But it's nearly not as impactful. The rotation is basically the same. Keeping Mortal Strike on CD, spending Overpower procs and using Slam/Whirlwind (with Fervor of Battle) with as a filler. Deep Wounds has little effect on the rotation at all.

Our cooldown, Colossus Smash is quite simple to maximize. Fit as many hard hitting GCD's into the window as possible. Such as Mortal Strike, Execute and Overpower.

The whole rotation is a bit slower. You get less rage per auto, Opportunity Strikes is gone, Archavon's Heavy Hand is gone, Dauntless is gone and Mortal Strike costs 10 more rage. You're going to be spending more time sitting on a GCD or two to keep Mortal Strike on CD.

But there are ways to combat this such as Charge and Bladestorming. However, the higher Tactician proc chance helps fill globals.

Bladestorm is really powerful now and might be used on single target for its full duration, but we'll have to see.

Execute phase is pretty simple.

Spam Execute, use Overpower when it procs and Mortal Strike at 1-2 Overpower stacks depending on talents/traits.

THIS IS STILL BETA, EVERYTHING IS SUBJECT TO CHANGE.

To sum it up

• Reliance on Colossus Smash is gone.
• Overpower replaces Shattered Defenses.
• Resets are still in the spec, not nearly as impactful.
• Slightly slower rotation without many rage generating/reduction tools.
• Bladestorm may be worth using for it's full duration on single target.
• Execute phase is largely the same, using Mortal Strike at X Overpower stacks/X Executioner's Precision Stacks.

Toolkit compared to Fury

Arms has the upper hand in low target cleave. However Fury looks like it's going to excel in the Burst AoE department with all it's recent changes. But that doesn't mean Arms can do really good burst AoE as well. It's similar to legion where Fury has more upfront damage and Arms has the higher potential.

Closing

Blizzard finally made the spec they wanted since the start of Legion. The spec rewards good gameplay and doesn't play like a slot machine. Of course there are some issues with BfA Arms, but they are very minor compared to Legion's massive issues.

Thanks to Vel for the much appreciated feedback!