I feel like there is a growing problem with ADC itemization right now.
The #1 ADC right now, Lucian, rushes Ghostblade and Black Cleaver, plus he is the first ADC to have a respectable banrate in ages. And now we hear of a Duskblade/Ghostblade MF build that is supposedly "destroying" Korean Solo Queue. If someone were to ask me, I'd tell them that this is the result of how hard early game leads are being snowballed globally, thus resulting in many games ending early before the ADC even has 4 or 5 items.
Infinity Edge, right now, is probably the most inefficient item to rush. Ever. Without it's passive it has 85% efficiency. Ghostblade, meanwhile, is 161% efficient when you use the active. Twitch is rushing it. Draven is rushing it. Lucian is rushing it, and now MF is. This build is becoming increasingly popular, and winrates are rising accordingly. MF, especially, has seen a big increase this patch, and this is with the Korean build becoming more popular. In fact, the Ghostblade > Duskblade > Black Cleaver build is the most popular path and has a nearly 7% higher win rate than the old ER + IE + RFC. Lucian's winrate was #13 on patch 6.6, and now he is #3. MF was at #10, now she is #2. (Using stats from op.gg)
And there have been many stat comparisons done. These builds are far more efficient and strong than the normal 2 item IE/ER + Zeal item. I've been saying for a while that ADCs that excel early game compared to others will probably be better this season, but now that these builds are popping up and seriously increasing the winrates of champions that can use them, I think more attention needs to be given to this.
needs to be melee only
Has half max stacks on range champs
is actually pretty fine,twitch still bought it even before the marksmen update
and 
have restrictions on them, but Riot doesn't want to have any more items with restrictions on them since it "creates restricting gameplay". As much as it sucks, we are pretty much stuck with marksmen abusing these things till they get nerfed and no one wants to build them anymore.
: Before the QSS nerf, there was literally no reason not to buy it. It had a decent build path, a large chunk of AD, and provided Lifesteal. Then you add the active on top of that.
/
: Go from being ignored by tanks to being able to ignore tanks. 45% bonus ArPen is huge. Mortal Reminder also shuts down healers way too hard given how easy it is to apply the GW debuff, and how cheap 
is.
: It's like the Zhonyas for AD, if it took all the steroids and then still cheated at the Olympics. Zhonyas gets to invalidate certain AD champs kits once every 120 (used to be 90) seconds, Maw gets to invalidate all Mages and a some tanks/fighters who rely on magic/mixed damage for most of their damage output, while still providing good offensive stats like ArPen. What's that, you got me low? Let's just passively pop a shield without me having to do anything, and get a steroid of AD and Lifesteal that doesnt wear off until one of us dies or runs away.
, EDIT: 
) (tell me if I've forgotten any), Champs who synergize with one item so well that they have to buy it (
), or Champs who scale with AS so well that they happen to buy crit as a secondary stat (
).
, 
and