personal thoughts are
crit/ss > det for an offensive build, hanging around in cleric as long as possible
det/ss > crit for a defensive build
i wont rely on crit for healing – even if it may look fantastic if you throw out a 14k vitra but well yeah... u know?
ss on the other hand is way underestimated by most of the community, it really can save the day taking care of f.e
tank busters and stuff or if you have to solo heal cause the 2nd healer is kissing the ground for whatever reason.
