Today, we have been given some insight into the details of these changes, and while some aspects seem promising, there has been much speculation that some fairly disastrous consequences will arise to nerf any positive that these changes may bring.
From this post at the official forums:
Elixirs now stack in two categories, Battle (Offensive) and Guardian
(Defensive) Elixirs. You can only have one of each type of Elixir up at a time.
As a result Elixirs now stack with class abilities such as "Arcane Intellect."
Four new defensive elixirs have been added. Two are on trainers, one is in
Halaa and one is in Cenarion Expedition. "Flask of Petrification" can no longer
be turned off during its duration, but it now will clear all threat from all
monsters for the duration of the effect. Though monsters may reaquire you after
the effect ends.
The cost to purchase Imbued Vials has been reduced.
The reduction of the vial cost is a much needed change, as a standard raid night was costing between 8-20G for the vials alone, for those of us on the cutting edge of content, let alone the farming time required to craft the necessary materials.
However, the Elixir changes, while seemingly will cut down on elixir usage, will only serve to drive more guilds to demand the usage of Flasks to compensate for the lost effectiveness of their members.
For example, as an Affliction Warlock, my standard raid consumable list looks like this for every pull:
Elixir of Major Shadowpower
10 Superior Healing Potions
5 Superior Mana Potions
On Severe DPS race events, I will add a Flask of Supreme Power into that
mix, but those events are rare, and often only during the learning phase of
Unless Blizzard retunes the encounters to account for these profession changes, they will be inadvertently forcing us to farm more rather than less.