This is slightly “old” news but the last new beta build reintroduced masteries. Masteries are derived from the mastery rating on your gear (which starts appearing at around level 82 I believe.)
MMO Champion give the following example:-
A level 82 player will get 1 Mastery point for each 93 Mastery Rating he has. This mastery point will increase the mastery bonus differently depending on the class, +1 Mastery Point doesn’t necessarily means a +1% increase to the bonus. (e.g. A Beast Mastery hunter with +2 Mastery gets +4% increased pet damage)
The elemental mastery reads as follows:-
Grants a 20% chance for Elemental Overload to occur. Elemental Overload causes a Lightning Bolt, Chain Lightning, or Lava Burst spell you cast to trigger a second, similar spell on the same target at no additional cost that causes 60% of normal damage and no threat. Chance to trigger increased further by mastery rating.
The Cataclysm Compendium has been updated to incorporate the above information.
Finally, on the subject of editing old articles, the Elemental FAQ also received it’s overhaul yesterday. Feedback is welcome!