It needs a rework. When the main damage ability is so inconsistent it can only be balanced around the average DPS of it, meaning that sometimes it’ll hit like a wet noodle and at other times like a run-away train. All of these numbers are contained in the average as measured over time. This means that in situations shorter or longer than the time the average is based on Arms will either under-or overperform.
All the situational damage modifiers to MS needs to go away and MS needs to hit harder than it does currently, with some of the damage boost being given to Slam, in return the utterly stupid hits possible with MS will be impossible.
With the damage being a constant then Arms can be properly buffed.
With the situational modifiers gone and there’s still a desire for them to do something have them generate the Rage for the spec or increase the amount of Rage generated to make the spec more fluid in playstyle.