Out of curiosity, how much of that do you feel is due to Riftmaker's design, and how much do you think that might be due to the general lack of items like Riftmaker in the past causing champion design to skew away from spaces Riftmaker might appeal to?
Looking at AD vs. AP bruisers, most AP bruiser-types (Gragas, Rumble, Sylas, Diana, Cho'Gath, Swain) tend to end up favoring burstier builds or solid tank builds, and my opinion for a while has been that the inflexibility of AP as a stat (compared to AD, which can be better focused on a specific role due to the additional tuning levers it has) has kind of limited the ability to design AP bruisers who aren't encouraged to go heavily tank or heavily AP. I think this, in turn, limits the appeal of longer-duration sustain bruiser items, because there aren't enough characters that have the pattern innately to want to buy an item that enhances it. Riftmaker on its own is an item that enhances the pattern if you have it, but isn't sufficient to create that pattern on champions who don't play that way naturally.
Specifically, the issue I see is that if we give AP Bruisers high ratios (like Sylas), they easily end up as burst mages/assassins, but if we give them normal AP ratios then we end up risking that our bruiser items are picked up by mages and assassins who can end up tankier than desired, which limits the space available to build items for extended AP fighters. Since we don't have an equivalent of base AD or base attack speed, and we don't really have interacting mechanics like critical strike, it's far trickier to create those clean itemization lines that allow AD Bruisers to have dedicated items and -- in turn -- a good place to sit in the class system. This makes designing those characters as true AP fighters harder, and then means that items aimed at AP fighters struggle because there aren't many true AP fighters.
Thoughts?