Well a good number of people are 85 and many of them have met the ilvl for heroics. However a lot of these people are finding that they have trouble running said heroics. These people have turned to getting every edge they can. Enchants are selling well but everyone and their mother is an enchanter. While there are a high number of Alchemists as well with mat prices as high as they are many people refuse to make items even if they can make a profit. Yet there are many consumables people are seeking out to make themselves for effective.
Tanks have found at times popping defensive cool downs just isn't enough and so they are looking for little ways to increase survivability and lessen the healers burden. Earthen Potion and Elixir of Deep Earth have both been steady sellers for me with the elixir having a larger return on investment but the Earthen Potion is selling all day in stacks of 10.
For healers I have found many looking to use Ghost Elixir however most have chosen to use this over the Earthen Potion to level and it is no longer profitable on my server. However I do believe most of the Mythical Mana Potions I have been selling to healers as most caster DPS have had minimal trouble with mana.
Potions and elixirs selling to DPS are all over the place although for one reason or another the ones proving to be most profitable in both numbers and profit margin are as follows. Elixir of Impossible Accuracy, Potion of the Tol'vir, and Golemblood Portion. Your server may differ but my point here is look at how people are leveling their Alchemy. If the crowd is tending to go with the same items to level then you may want to look into the options that are not as popular. Although I would make sure they provide some buff or use that people will actually be looking for.