Picking Apart Rageblade
I heard that Riot still isn't happy with Rageblade. So, I'd like to talk about this item in-depth and why Riot wants to revisit it.
First, let's see who the item is for, and who is actually using it. To determine what champions are meant to use it, we'll look at its stats and features.
AD - AD champions
AP - AP champions
Attack Speed - Champions with high AD or on-hit damage
On-hit damage - Champions with high attack speed, or ways to apply on-hit effects quickly/uniquely (ex. Renekton or Ezreal)
Phantom hit - Champions with on-hit damage.
One other thing I should mention is that the passives require stacking before you unlock the item's full power. This firmly cements it as an item either for DPS champions, or splitpushers that can stack it before combat.
From all this, it's hard to determine just what champions should be using it. Is it AD+Attack Speed On-hit champions, like Master Yi, Vayne, Nocturne, or Jax? But then why is there AP on the item? The usefulness of this stat widely varies for AD champions. Master Yi has one AP ratio on Meditate, Vayne has none at all, Nocturne has minor scalings on E and his passive, and Jax scales rather well with AP. They generally don't want the AP, or view it as a minor perk. Fighters also don't like AD multipliers like Rageblade has because they don't build as much AD as a carry.
The attack speed and AP combination in particular is really weird. This is the core identity of Nashor's Tooth, used by Kayle, Kai'Sa, Teemo, Azir, Kog'Maw, AP Varus, and Diana. That's everyone; it's a niche item. AP is usually associated with burst, which is antithetical to attack speed, so only a handful of champions are designed to utilize both at once. However, just as AD champions don't want AP, AP champions usually don't want AD.
Last, I should talk about Phantom Hit. This is where the stat mixture of stats starts to make sense, because all the AD and AP champions I mentioned above value it. Many champions in the game have on-hit damage with no cooldowns (in contrast with Sheen, which does not work with phantom hit) and would want this passive. But it comes with strings attached; it's expensive, it has no utility, it probably has a stat you don't want, and it has to be stacked in combat before reaching full power. These qualities make it very unappealing for most melee fighters, who can't easily stack it in teamfights, can't afford it Rageblade, and don't want AP. I mean, you can make expensive items for fighters, but there needs to be some defensive stats included so that they're as tanky as they need to be when players start grouping.
Some of you might remember when Sheen and Trinity Force had AP instead of CDR. They were changed because the champions that liked Sheen and Trinity Force were all AD champions with varying AP scaling. Gunblade used to have a weird split of AD and AP, now it's more skewed towards AP. There's just not much interest in hybrid AD+AP items for most champions, very few want both and most just maximize one or the other.
So in total, we have 3 groups of champions that want this item or an item similar to it:
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Marksmen (and Master Yi) that just want AD, attack speed, and phantom hit
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Fighters that want phantom hit, AD, attack speed, and some defense or a cheaper item
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AP/Attack speed champions that just want attack speed, AP, and phantom hit
It serves some champions very well, but it could be so much better as more focused item.

all became obscene balance problems during at least one if not all of these item peaks. Many of them were nerfed instead of the item.