Doesnt reducing defence means taking more damage from standard attacks, and losing more life..so more or less he is again his squishy self in initial rounds?

Why not go +hp - attack...since his mystery damage is more based on ninjustu...or just -ninjutsu since he scales ninjutsu..

I tried out to find how he scales...his description says "sccales on taijutsu damage"..Everytime he gets taijutsu hit its shows +ninjutsu +defence...Does it increase by a fixed percentage or does the percentage varies by damage of each hit is unclear? I belieive fixed percentage increase per hit.