Depends on matchup. Any hard engage supports like leona, blitz, nautilus, etc you want to run arcane comet into since you are trolling if you try and auto them too much. Most everything else you wanna run hail of blades into.
During mid-late game champions are more tanky if you're not super ahead on levels and items with ashe. Do not rely on her AA because you have no escape skills and you will get caught by trying to AA, so I would prefer Q last.
