Unlike standard mids who can go hybrid offensive/defensive items like Rylai's and Liandry's (these items don't fit diving melee mids), I think this is a bit lacking for melee burst APs. Most melee APs want stuff like LB but are too squishy if going it earlier. Unlike Ori or Xerath who have some usefulness from a distance, the diving mids just seem incapable of going full AP without actually making their late game WORSE. You'd expect harder scaling but it actually just becomes too risky to play so it doesn't matter (you need HP and resists). Even Fizz, the slipperiest of them all gets Zhonya's or Protobelt first and often dips into Resolve. These champions just can't function without some tankiness and there aren't many good tanky but damage items. Abyssal just got nerfed this patch and while it is good, it's awkward to build and only vs magic damage.
What am I suggesting? I'm not sure but I was looking into the max scaling builds for assassins like Ekko and realized that the big ticket items are hard to fit in without being so squishy that it's unviable or giving up Sheen damage. It's even worse if I want to o Nashor's and LB in the same build.
Example for JG Ekko:
The funny thin is that this is the highest DPS build possible for him but it's just totally unviable. If it works, you'd probably win that game anyway and it doesn't matter what you build. If it's an even game, you just get melted in 2 seconds. I once tried to throw a W on the enemy team and I died mid dash towards my W. What a waste of 16k gold. I want to go max damage on a lot of these melee APs but it just doesn't seem to work. I even tried RoA for some tankiness but it delays the spike so much for minimal benefit that I feel forced into these mid game items. Meanwhile, Anivia and other mids have no problem building for some incredible scaling and even taking Gathering Storm on top of it and maxing CDR + being tankier than me.
I sort of like IBG but it has WAAAY too much mana that I don't want or need. If that mana could be halved and instead I get a Ruby Crystal of HP, it would already be better.