It seems as though the optimal for dealing best overall damage will vary slightly form class to class, and also on how you trait your WS.
Most people here seem to agree that being moving will always increase your overall output, the disagreement seems mostly to be on how much movement.
My own observatiosn and testing leads to this conclusion, personally:
As a hunter, the optimal for damage output lies in two clicks of fury; skills traited for their shortest possible cooldown, with the setting that stops your crit buff falling off some of the time, and alternating establishing with other skills every second usage, as rapidly as the skills come off cooldown... also to always be behind the boss, and as importantly, to have him in your direct 90 degree frontal arc, so that your auto-attacks continue to slip in between every skill... you can fire your skills at 180 degrees, but your auto will only fire in quite a tight frontal cone; keep it facing. Keep moving at the walk seep, since you'll only build two clicks of fury between each skill, you don't need to go any faster.
That's a whole heck of a lot of variables for just one class though; that's sort of the point. The optimal for damage output, for how much you should be moving, and -how- you should be moving, is going to be different class to class, and build to build.
One thing that is universally helpful, though, is how you move the target. Most classes can gain their optimal damage when they strike from behind directly; whether it's actually positional damage, traits that apply extra bleeds from behind, or simply the negation of the targets BPE... so, movement wise, if you're dpsing, chances are you'll want to be trailing along behind the target, moving at your optimal, while still keeping his behind in your sights... which means the person holding his agro can make things more optimal for everyone by essentially "laying out" the boss. Rather than running him in a circle, or strafing around him, as most seem to do, if you're holding the threat, move ahead and lead him, slightly faster than he's going, and weave; running away from him, just fast enough that you can keep ahead, while weaving just enough to keep firing your own skills constantly. This'll keep him running in a straight line, and let other people trail his back more effectively. You can turn him around and take him back again if you're worried about distance and resets. If damage threat is all that's in play, and no-ones using other threat skills, your 'leader' will probably lose the threat sooner or later; it'll be slightly fury augmented skill usage, against slightly augmented skill usage plus autos, at minimum... this is no biggie, so long as the new leader then just takes over the leading, and the old leader becomes a trailer.
Just my own observational notes hope it helps.
-Niara