The gems from the events are only CL 10, with CL 15 coming from the Mabar Items. The Snow Elemental Gem has no ML, the Cove Gems are ML 4, and the Mabar CL 15 item is ML 8. They aren't really all that powerful, and they would be fairly useless once you got up around time to run the Shroud (if not sooner). They would, however be something useful for lower level Rogues and Arties to spend trap parts on. Or pass to lowbie alts.