There may be a situation where you don't have enough rage to use an offensive ability (which automattically starts auto-attack) and you're not already auto-attacking, so activating autoattacks would allow you start dealing damage (and threat) earlier and help a bit with rage generation.
I personally macro /startattack into my main abilities, that way I can use those buttons to start auto-attacking even if I don't have enough rage to use an ability.







Bookmarks