Scale Shot Haxorus is bad. Scale Shot's average damage is less than .67x that of Outrage, I believe ~72. The speed boost is useful, ofc, but it leaves you more vulnerable to physical attacks. The two advantages are: it's easier to SD, since you'll get a speed boost, and you can run LO instead of Lum Berry since you won't get confused. I don't think this is worth it due to Scale Shot's inconsistency compared to Outrage (not to mention LO recoil compounding your decreased physical bulk).
Outrage could leave you vulnerable to fairies depending on when you clicked it, but I still think it was better than Scale Shot due to its immediate power. Scale Shot's average damage does (barely) exceed Outrage if you compare +1 Outrage to +2 LO Scale Shot, which is a possible scenario, but Outrage could also function with Swords Dance. And given Haxorus's already tremendous power, I don't think the possibility of getting a 100 or 125 BP Scale Shot for increased power is worth the relatively high chance (1/3) of getting a 50 BP scale shot and failing to kill your opponent then getting killed yourself. Outrage at +1 killed most neutral targets anyway.
Outrage certainly has its own drawbacks (Lum Berry, locked into a move), but it's superior to Scale Shot. Especially on Dragon Dance variants.
Edit: And ofc, bringing back Outrage would also mean bringing back Dragon Dance.