He's there for the sole purpose of attacking and igniting. But your point is right, he can be easily killed even by f2p teams such as kushimaru blitz and 3rd raikage blitz. Well if you want to make him tankier, you c*e your magatamas, charms, refines, runes and etc. In eight inner gates, improve his critical, injury, resistance, defense, control and damage reduction. You c*so shield him or apply some healers. If you're still not satisfied you can wait for his SB. There are many options, but tbh I also think that he should be more defensive.