I've been 2 orange essence away from getting Headhunter Akali for a few months now. I've opened a number of chests, and still haven't gotten anything to disenchant into orange essence... 
It would be great if the essence could be obtained alternately, because obtaining the keys/chests can be super grindy.
I wish so too, I'm 500 essence away from Battlecast prime Cho'Gath. The one time I get a good skin, I don't have enough essence for it, and the boxes I open are all champions. (Taric and TF) [zombie-brand-facepalm]
Weird, I've gotten enough for HexTech Annie, Project Yi, Battlecast Cho, Super Glaxey Rumble, Project Fiora, Firefighter Trist, + some other cool skins.
