What is the question, really? You use this when you need the solid DT-8% (as opposed to the fluctuating value of Creed+2), the TP gain is too small for it to be a factor in the decision on when to equip it. The haste from the set is nice and all, but it's not really the first consideration when building defensive sets, and there's plenty of better head/body combinations if you're looking for an offensive setup.
If you were looking for a more detailed answer, ask a more detailed question.
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.)