I think I understand what Riot is doing with the MYMU

Lowering AP on items and handing out more CDR: Trying to reduce the power of burst mages, perhaps? Also, most mages have a tendency to "well, that's one spell rotation. Only 10 more seconds till the next!" In team fights, so maybe they're hoping the CDR will alleviate that.

Adding items with spells/utility attached to them: Possibly, in compensation of reduced AP on items, Riot is trying to give AP champs MORE buttons to press in a team fight. In other words, AP champs get more spells, so they can use their AP more often.

Those weird-ass RoA changes: Trying to bring Swain back into the meta. ALL ABOARD THE SWAIN TRAIN!

Remember, all this is speculation! Feel free to add your own insight.