Just want to point out that attempting to sneak up on a boss doesn't work. They detect you and remove your Hide status before you get close enough to use TA. You might be able to get in TA if you Shukuchi + TA quickly enough but I doubt it. In order to make Hide more useful though SE added a new effect to it with SB: reset Ninjutsu cooldown when you successfully use Hide. So whether you actually get in the TA via hiding or not, hiding before a boss battle ensures you can get in a TA since Suiton can be used immediately.