I just got berated by team members today for using the LB3 on Ninja when it came up during Byakko normal after the phase transition, due to it being "way too early". I judged the healers to be doing fine, no deaths or anything and it's not like Byakko gets suddenly way harder after that point, so I did it. Was able to get another Braver towards the end because of it. However, this goes to show that public opinion may differ quite a bit sometimes, so even if you go with all the advice in this thread, be prepared to get flak either way from people who have very set ideas about it.