AP inefficient Item Curve
So I just noticed that for Ap carries, the item curve is inefficient when compared to ad carries. In order for an AP carry to get the big damage out they have to farm for 1600 gold to get anywhere good. 3 core items are 1600 gold, and the one item that is significant for countering an AD burster is extremely expensive.
Compare that to AD champions who carry. Most assassins just grab a brutalizer, and a blade of the ruined king which both have extremely efficient cost curves. Even the AD defense item against AP champions is better. You can get some good MR and damage and shield for 1350. Which builds into Maw after 875 and 975. Which is way more efficient then compared to the 1600 then 500. That 1600 gold period is of you not getting more powerful. Now, Athenes Grail is a good example of a good power spike. Its efficient, but it doesn't help champions who don't need that mana.
I feel that the items need a significant rework of their cost and what they do. I think the reason the meta is currently revolving around ad assassins is because its more efficient to play them, rather then to play AP mids. This is more apparent in Solo Q then in team games, because team comp is more important.