epic JC gems are not in patch 3.1, probably patch 3.2. So JC is "the best" for at least another 6 months. There are 4-5 new epic gems in patch 3.1 you get from fishing, but they are unique-equipped. Second best would be LW for bracer enchant, inscription for shoulder, or tailoring for new cloak enchant (+250 spell dmg, 45 sec hidden c/d, effectively making it +83 spell dmg assuming always casting).