Here's the thing, though. ROA is only good on AP tanks (and usually not built at all), Archangel staff is more of a niche item, same with Lich Bane. Morellonomicon is a better version of Holy Grail. Nasher's Tooth is also Niche, Revolver is very niche (same with Will).
This leads you to the 3 120 AP items, then your choice of Linadry's, Ryali's, and Abyssal (for 2). This is the same for burst and sustain mages. Usually, burst and sustain mages have a very similar build. These item changes are attempting to change it.
When I play a mage, I would love to build Liandry's, but there's usually a better option. When I play Teemo, I'd love to build Nasher's Tooth, but the 60 AP is too low. As Annie, I would like to build ROA or Archangel's staff, but I'd rather have more AP. With these changes, I could see myself having Archange's Staff as a core on my Annie and ROA as a core on my support Annie.