I am a bit nervous that the devs have not addressed this issue yet. If you are in a guild that it not level 20 Old Sharandar is about the only way you can get Fey Trinkets / Vouchers for guild upgrades. Unless they plan on selling vouchers for gold or AD somewhere the only source for fey trinkets will be lock boxes. This is really unfair and problematic for guilds.
Boudica's Sisters - A Guild For Introverts