To keep it short and simple, I've been an alchemist since vanilla WoW, and while many professions have been receiving constant improvements here and there, alchemy has been more or less the same since Burning Crusade (the main exception being the Vial of the Sands). Since BC, there have been a lot of alchemy-themed bosses in dungeons and raids that have interesting abilities, and all sorts of alchemy tools that we get to use for quests, but there's nothing comparable that gets made by alchemy.
Currently, a lot of alchemy is just a preparation elixir and one gulp in combat, but that's not exclusive to alchemists. Alchemists don't really stand out much since everyone else can use most of their products regardless of their profession. I'd like to see some fun combat options for alchemy get included. How about throwing vials of acid for a quick AoE burst, or injecting some alchemical disease into your target for an extra DoT? Why not homonculus combat pets that fight for a brief duration like the engineering dragonlings or jewelcrafting trinkets? Or if we have to stick to drink only, how about a potion that transforms you into a juggernaut for a short period of time? I'd like to have alchemy be something more than a cash cow.
Blizzard has barely scratched the surface of alchemy, but it seems they're not really interested in going much deeper. Or that's my opinion anyway. Post your thoughts below!