You'll be at a serious disadvantage offensively with uncapped skills, even with the Arts bonus. Just keep XPing in Abyssea, you can cap them there. Just don't be that guy spamming Stone Bio and Dia endlessly; having underleveled skills is not an excuse to be completely useless.
Also, AF body/legs just grant skill+15, they don't change your skill rating. The distinction matters.
RDM can attain an almost static 50% reduction to recast time, SCH can over shoot this for a total of 60% reduction under Alacrity (provided you are wearing loafers and keeping dark weather on yourself)
MACC is a joke, any job with access to mage gear can hit close the MACC cap on legion mobs, which is why my BRD/RDM can land slow/para/blind despite having only 150 skill (from /RDM.)