As a healer BT would benefit from a HP increase, however he only heals 27%, so it wouldn’t make a big difference.
He also has an amazing 48% attack buff. Spending the emblems there would boost him, but it’s his lowest stat and as a healer/tank he should focus more on staying alive. On the other hand the fighter class benefits the most from an ATK increase.
Defense is his best stat, but is not affected by his special.
What do you think? Attack primarily and Def secondary?