In my opinion the best specialization is all a matter of how much effort you plan on putting into alchemy.
From what I have read all specialties have about a 20% chance to proc multiples.
If you're the type that mostly does daily quests for money, and you don't want to spend a lot of time collecting herbs. Or if you prefer to sell your herbs, then Transmutes is probably best for you. On the plus side it takes the least effort because you will mostly be transmuting for other people who will supply mats. And when it procs it procs big. 1-4 extra primal mights at 75-100g means you can potentially make 400g extra for doing a transmute. On the down side you can only transmute once per day. and you won't proc 5 on transmutes very often. at a 20% proc rate you'll see extra transmutes about once every 5 days, and will probably average 2 extra when you proc. So your profit here is looking like 200g per 5 days.
With potions you'll be spending a lot more time collecting mats, however the amount of extra money you can make is only limited by how many herbs you want to collect. Lets say for example you're a Potion master making Healing pots. On my server a healing pots sells for about 2-3g, and the mats are pretty simple. if we assume the same 20% proc rate you would have to make around 350 potions in 5 days to make about the same profit as transmuting. 70/day is a high number to keep up with, but this is just the first potion I picked off the top of my head without crunching a lot of numbers as to what would turn a better profit. It also doesn't account for if there are any potions which could be sold for a similiar amount to what the mats would cost so that you could just buy a ton from the auction house.
Elixers I would only do once you have discovered a few flasks, however in my opinion this would easily net the most profit. On my server most flasks sell for about 40g each. and if you're online at popular raid times you'll have no problem getting people to give you mats to make flasks. the profit per proc will be about 1/2 what you can get from transmuting, but you can easily do more than twice the flasks to make up the difference if you have the right recipes.
From what I have read all specialties have about a 20% chance to proc multiples.
If you're the type that mostly does daily quests for money, and you don't want to spend a lot of time collecting herbs. Or if you prefer to sell your herbs, then Transmutes is probably best for you. On the plus side it takes the least effort because you will mostly be transmuting for other people who will supply mats. And when it procs it procs big. 1-4 extra primal mights at 75-100g means you can potentially make 400g extra for doing a transmute. On the down side you can only transmute once per day. and you won't proc 5 on transmutes very often. at a 20% proc rate you'll see extra transmutes about once every 5 days, and will probably average 2 extra when you proc. So your profit here is looking like 200g per 5 days.
With potions you'll be spending a lot more time collecting mats, however the amount of extra money you can make is only limited by how many herbs you want to collect. Lets say for example you're a Potion master making Healing pots. On my server a healing pots sells for about 2-3g, and the mats are pretty simple. if we assume the same 20% proc rate you would have to make around 350 potions in 5 days to make about the same profit as transmuting. 70/day is a high number to keep up with, but this is just the first potion I picked off the top of my head without crunching a lot of numbers as to what would turn a better profit. It also doesn't account for if there are any potions which could be sold for a similiar amount to what the mats would cost so that you could just buy a ton from the auction house.
Elixers I would only do once you have discovered a few flasks, however in my opinion this would easily net the most profit. On my server most flasks sell for about 40g each. and if you're online at popular raid times you'll have no problem getting people to give you mats to make flasks. the profit per proc will be about 1/2 what you can get from transmuting, but you can easily do more than twice the flasks to make up the difference if you have the right recipes.