Essence Reaver still a noob trap, and will remain so until either...
a) Mana begins to be an issue for AD champions past the laning phase. Unless you fail really hard, not even Jayce or Urgot will have [B][I][U]enough[/U][/I][/B] issues with mana to warrant wasting a slot on this item over BT or BotRK. Not even Ezreal gives a **** about this item, because even if you're going to blue Ez build, Muramana and the Iceborn Gauntlet provides MORE than enough mana already. If it didn't provide enough mana, Blue Ezreal would never have been a thing in the first place.
or
b)The item's build path makes some god damn sense! Champions who would consider building this item in the first place are ridiculously mana-hungry, and often times [B]that mana starvation is by far the most pronounced during early game.[/B] Therefore, any champion desperate enough to even consider this item would have gotten a Tear to build into Manamune instead as that build path atleast provides you with mana sustain [B]when you need it[/B].
Maybe if the item restored mana based off ability damage as well that'd work out. People would ***** and moan about Jayce being "oh so OP", but those people wouldn't even realize that he doesn't need the item to consistently poke in the first place, and that he isn't constrained by mana late game, but rather his insanely high CD's. So this kind of change, as drastic as it sounds, will only really help Urgot.