Don't forget that Alchemy can be quite fun, I got a x2 truegold proc from being a transmute master the other day and I got people in the guild who had up to x6 procs
But elixir/potion/transmute masteries aside, yeah, it's "just" for the improved duration (2 hours instead of 1) and the increased benefit. But in that sense, you can also tailor it to your needs. Resto? Get more intellect from your flask. Enha? Get more agility from your flask.
On top of this all, alchemy is extremely easy to level and one of the cheapest aswell. I am going to drop mining for alchemy soonish, as leveling blacksmithing past 425 is an absolute waste, unless you want to craft BoE stuff for money.
EDIT: there's also the new Alchemy trinkets coming with patch 4.0.6, so in case you don't have good 359 trinkets yet, there's another reason to pick alchemy.