Correction: More Valor hotfix hasn't gone out tonight. It will get pushed with the next raid reset.- Greg Street (@Ghostcrawler) December 4, 2012
This means that when the raids reset tomorrow (Tuesday), everyone will get the enjoy the higher valor drop rate. The changes are not taking place today, because as Ghostcrawler puts it: "There was some concern of causing ill will among people who had already finished raiding for the week."
As far as why the change happened, Ghostcrawler says:
@shadesogrey Sympathetic to the argument that 16 bosses is already a big time commitment. Different world from small tiers like Firelands.- Greg Street (@Ghostcrawler) December 4, 2012
Warlocks, paladins, and monks also received minor changes. The full notes after the break.