I want to propose to make better the arts from swell brain.
What i mean is about remove the fixed stats and make it increase the stats based on your current stats as Lifeline does (but swell brain will continue giving bonuses only to two stats, so it wont be like a second Lifeline)
Moreover, i want to propose to make it be only one Art that increase DEX and SPR. Both stats give damage on critical hits (physical critical damage and magical critical damage) and it would be usefull for healers as well.
The reason is that only 50 points on two stats is useless… I think that it doesnt makes a real difference on the character/party.
Moreover, this skill (and i think that others from some support classes) could have an attribute to make it be applied only on the caster but doubling the bonus or something like that (like the “pass” skill from chronomancer for example). There are other skills that could have an attribute/art to reduce the effect that it gives to the character and apply it to the party as well.
I hope you like the idea!! 
Cheers