Just talking about assassin items again.
Just a quick something so you can understand the difference between the items.
AD Assassins have: 71 lethality, 24% Total armor shred (Getting buffed to 30%), and 35% Bonus armor ignore. That's all 3 dirk items, the Pen Rune, Black Cleaver, and then typically Lord Dominiks. Ghost and Duskblade of course giving them 20% CDR while BC covers the rest.
Most assassins won't go the full 3 dirk items and instead go Ghost and Duskblade, then opt out their final slot for GA. The build is Gold efficient, Build Efficient, covers every stat they need/want, and that's not even touching on the other insanely strong passives and actives that these items bring, mainly Duskblade. Keep in mind that that isn't even a weird build, the standard builds for assassins mid lane is infact Duskblade>GhostBlade>Boots>Blackcleaver>GA>Lord Dominiks. Run by Talons and Zeds all over the place, and even champions who aren't supposed to be assassins like Riven.
AP Assassins have: 38 flat pen and a 40% total MR ignore. This comes from Liandries, Pen rune, Sorc shoes, and Void staff. Liandries is inefficient because assassins neither need nor way any of the other stats besides the Pen and AP.
Blasting wand is already build inefficient, sitting at 850 gold with no tier 1 items to buy into it with. spending 400 gold on a ruby crystal which offers no offensive stats also furthers the inefficiency in the build, this item was afterall designed for mages to get better DPS towards tanks.
Sorc shoes hold 15 pen but completely seal off any options to choose utility/defensive boots unlike AD assassins. No tenacity, no ability to get ninja tabi which would massively help against the already advantageous AD matchups, and no Mobi's for better roam potential.
Finally coming to void staff which is fine, but it still requires a blasting wand which is not good for builds at all.
In general the AP itemization is filled with inefficient items to build like blasting wand, lacks CDR and Pen, and items that would be good are bogged down by the previous problems but added gold inefficiency due to unwanted states, mainly speaking towards Liandries and Gunblade.
AD itemization on the other hand never has anything wasted, grants its users an oceans worth of pen, has items filled with cheap long swords, and offers an overwhelming amount of strong passives and actives that fulfill both added damage and utility.
Arguments against this are typically: "AP Assassins deal more damage". Not really true. With the differences in scalings the damage is actually fairly even, and when you add in auto attacks which are supposed to be a primary damage source then it starts to balance out very quickly. Once you throw in tons of pen then a massive gap appears.
"AP Assassins have more utility". Define utility. If you mean mobility then all AD assassins have an insane amount. Talons is one of the best in the game. Only case where they aren't the best is in Rengar who makes up for it with increased tankiness and a free cleanse from his W + massively higher than normal damage.
if you mean CC and such then all I can say is Assassins aren't mean to be utility focused in the first place. Depending on the champion, having a single CC is fine, but if the champion is specifically gated so that they sacrifice damage in return for utility then they fail as an assassin.
AP Assassins have been long overdue for proper itemization. Since the whole point of pre season is to give room to completely demolish the game with whacky or outrageous changes, why not use that opportunity and try implementing some changes now?
