I finished leveling my Alchemist to 60 the other day, seeing as how I had an overabundance of levequests, and spent several hundred thousand gil on materials thinking that I could make it all back later on. But I've run into a problem. The potion I wanted to mass produce, max-ether, requires me to go to the Diadem and do my botanist thing there. I've got the class skill and the gear, but nobody goes to the diadem anymore, resulting in prices as high as 90,000 for a stack of 10. Then, I'll have to level my fishing to 60 (which I died a little inside when I discovered that), track down an ephemeral node, acquire the other 3 more mundane items and make sure I keep on top of my cluster farming.
It also occurred to me that I've never actually seen anyone using potions in a fight, or at least, not to any noticeable degree. While tricks of the trade and comfort zone are nice, I can't help but feel like I wasted a good chunk of personal resources on leveling a trade skill that really can't do anything for me because of the current state of the game.
TL'DR version, what good does alchemy actually do?