0.15sec in some fights, can make a difference, in burst dmg on take, or dps, or both, I can say the same about determination.

It's not 50-60 more determination, that does like 10 mind, that's gonna save someone or make the fight easier.

I even feel that 0.15sec casting speed can be more useful than 50-60deter that is like 20more heal on a cure, or less.