My 2 cents

I never set flash and that's a personal pref, if you are coming up on a set of mobs using a voke far enough out you will generally group them together as they run to you, or if you just run thru a set of mobs and overpower once your past them you will 90% of the time hit them all.

When it comes to TP issues you can sub in mnks Haymaker counter attack which is only 40 tp. When you are being attacked by 6+ mobs you "will" dodge attacks very regularly, almost enough to keep using it back to back, to add to this it will not break combos.

Not only will you gaining tp back after you have exhausted all of it using overpower, you will also be throwing a 20% slow on mobs while using Haymaker.

Like I said its personal pref, and you will sometimes not hit everything with your overpower ( mages standing away from pack ) but that's fixed with a simple tomahawk. Flash to me is wasted potential compaired to the extra damage from Haymaker and the slow debuff.