Its hard to read this guide without cringing alot you have left out many details and overlooked things that should be blatantly obvious to anyone who tries to use your guide.
Volatile Fire
For starters for Volatile fire you have mentioned fishing? A secondary skill most people won't bother leveling. You also failed to mention that you can obtain volatile fire from mining and skinning, You also failed to give an alternative place for farming the fires.(Twilight Highlands
http://www.wowhead.com/npc=48016 ) There are other enslaved fire mobs to the north west next to a quest mob they have a higher drop rate but a frustratingly low spawn rate for a proper farmer.
As far as
Volatile Air goes your mob location is correct. However u failed to mention that engineers get the electric static condensor "
http://www.wowhead.com/item=67494 " and can mine, skin and herb for airs. You also get Volatile Earth and Water from mining and skinning as well.
You also failed to mention the alchemy potion of treasure finding which causes mobs in Cataclysm to drop a tiny treasure chest that always has gold and sometimes has cloth and volatiles.
I'd also like to add that you stray away from farming the enslaved elementals in twighlight as they are bugged and if you misclick you probably wont be able to loot them.
Why did I take particular interest in this guide? I sell the Vial of Sands on my realm and I need to gather the mats myself and have been farming for the volatiles a lot. I didn't want to be a dick but I found your guide lacking and incomplete.