I recently purchased Advanced White Indestructible Crystal, as I like to tank, and finally got around to farming credits for this.
I loved it on my guardian and went to roll another one, in time for the new expansion only to discover that, despite it being a cartel crystal, the level restriction is level 50.
I know this might not seem like much of an issue, but making all cartel crystals use the same level restriction would make sense, and enable those of us to use the crystals we want ASAP.