Patch 3.0.8a (undocumented changes)

General

 * The mailbox located in Havenshire in Plaguelands: The Scarlet Enclave now disappears during the last phase of the Death Knight starting chain.

Mage

 * Arcane Missiles now consumes the Arcane Blast buff instantly so that you can no longer cast Arcane Barrage at the end of the channel to "double dip" in the Arcane Blast buff.
 * Glyph of Arcane Blast has been changed to 3% per stack.

Mage

 * Glyph of Arcane Blast doesn't apply its bonus damage to Arcane Missiles. (Source) ("This is a bug likely caused by the previous two changes. Such is the risk of making changes quickly. We can hotfix this bug out though." )