Posted this in another thread but I feel that with what was given Yoshi.P has a lot of routs to go with this. But currently this is what i am speculating.

To be honest I don't think he is defending us, if that where the case the bubble he makes wouldn't have to be that big, I think there is something behind him that we are unable to see that he is protecting with his life. Personally I think the Primals are the ones that will us their powers to save us, It is well known that the Garleans are out to kill off the Primals because they have gotten in the way, and fear their power. Also I would not be surprised is Yoshi.P goes the Kefka rout and is using lesser primals to fuel their Magitek, since its stated in the lore that the Garleans have no aptitude for magic which begs the question, if they have no aptitude for magic how are they making magitek. This will lead to as a summoner you are freeing the lesser primals (Fenrir, Cait Sith Typhoon) and they in turn become your loyal companions. All I can say is that I am in anticipation with the sheer amount of possible story routs they can go not only for the biggest battle in FFXIV history but the bringing of the new classes.