TA is more useful, as it gives a 10s damage increase debuff on the target, so your whole party benefits. As an opener, it's ok for dungeon trash mobs, but you'll want to at least make sure Huton is up when you start a boss battle. All the mudras share a .5 second cooldown, followed by a 20 second cooldown after using Ninjutsu. If you cast a mudra and DON'T use ninjutsu within 5 seconds of the last mudra cast, the ninjutsu cooldown automatically kicks in.