It is bugged for melee also.
Did small testing with a 1-3 dmg range dagger, that after all was said and done was hitting the Razellikh servants for 142-144, no +AP proc was used.
White dmg max crit= 288
200% crit.
SS max crit= 295
204.89% crit.
Easy test that shows that they tampered a little bit too much with the meta gem.
Edit to add a link:
WoW Forums -> [BUG] Relentless Earthstorm Diamond MELEE