Tailors, get you the cooldown the same as Alchemists.
I believe a zone was phased, so you'd need to level them close to 85th.
Alchemists are fine at 75th, and living in Stormwind/Ogrimmar or even Shatt/Dal (as they're Sanctuaries and thus provide immunity to Ganking) is fine.

Jewelcrafting probably provides a larger benefit then Tailoring, on a per toon basis.
The big thing is the JC daily, instead of the transmute.
You'd also get epic cuts for gems faster (several at once), which is more gold if you had enough alchemists to provide transmuted gems.