Before you read this post and start QQing about how much money you can make in WoW with alch, I advise you to calm down and reread the title of the thread. I make lots of money on alch, that's why I have 3 alch. All of which are xmute masters; however, my main is JC/BS. I would never have alch on my main and this is why...
What do you personally gain that no one else does in raids?
Mixology, double the duration of any elixir or flask. Mixology is a waste when cauldrons are out. Providing you have the guild rank for max charges and duration, guildies flask will only last two hours while yours last 4 hours. The guild is going to have to redrop another cauldron, so the benefit of your mixology is wasted.
What else do you gain?
An alch only trinket, but once you get geared that trinket is trash. It's only good for alts or when you first ding 85.
You get to drop a cauldron for the guild!!
Gratz, you're like a mage. Your raid doesn't need and alch for raid. You can have an alt drop one at the summoning stone. My guild has an alch, so she drops them in our raid. In our alt runs we don't have one at all, so I bring one of my other alts to drop cauldrons at the summoning stone, then I switch back to my alt.
You get to make a Flask of Enchantment for arena and 5 mans!
I redirect you to the title of the thread. During raids you'll never use that.
If you want to make a lot of gold, but are willing to sacrifice benefits to your own character then alchemy is for you. Alch are like tanks and healers, everyone takes them for granted. They resupply your guild banks with pots and flask, but outside of that, the person with the profession really doesn't gain much from a raid pov.
EDIT: So the tooltip doesn't show up for me to show the increased benefit from the profession. Disregard this thread. I apologize for wasting 2ms of your life.