Logging on with a scout character then swapping for your "real" character if the coast is clear = not kosher.

Logging on with your main character, realizing there's nothing you can really do, then switching to an alt (or just staying offline) = mostly okay (*).

(*) Contingent on it actually being <i>accurate</i> that there's nothing you can do. If there's one enemy online you can hunt and he's not grouped with the one guy hunting you that you have no chance against, then that's a situation where you might want to stay online. Hunt the guy you can kill and avoid the guy you can't.