After 11th chain completion i am pretty sure the end rewards are wired in a discriminating way.
Ie: A sorcerer wont receive elemental essence ring, and a fighter wont get the plate. (not sure about the figter only 5-6 completions with her)
Suggestion: make these items available in other end chests or dungeon rares. All the items that are currently end chain only!. As a furhter improvement if you are into that anyways, you may remove the korthos sets, they have nothing to contribute to lvl 5-7 players.
I dont think you should go this desperate on selling shared banks and seems like you are restricting players who own/earned the content.
Frustrated players wont spend money on your game, ...on a side note to your genious* marketers.
*you know what i mean
This shoul optimally take place with U11 or in a patch soon after