End Game ProfessionsFollow

I've been happy with tailoring/enchanting. If you're leveling both as you go (I'm assuming you'll be at least somewhat funded by other characters) you can DE all the greens you make for tailoring skillups and get enchanting mats from those, which helps boost it a bit. I've done fine at making money from both professions as well, which helps fund leveling them up.

But tailoring isn't as big as it used to be. The only tailor-only thing at this point is cloak embroidery, which is meh fine. The epic tailored items aren't anything all that exciting, and they're BOE anyway, but they still make good starter gear. Plus the ease of making big bags can be nice.

The enchanter-only bonus is ring enchants; +19 spellpower to each ring can be a nice boost when you're starting out getting geared and it's a super cheap enchant. I find being able to do my own enchants convenient in any case.

That said, almost every profession has something useful for priests (Titansteel Guardian: pretty!), but overall I'm finding the crafted epics currently in the game to be pretty mediocre. None of them make any profession a must-have for anyone. I'm hoping some more interesting tailoring recipes are in the works for future patches, since at the moment tailoring pretty much tops out at 445 and there's no real reason to push to 450.

Strictly speaking if you want the best endgame professions you can't take the mat gathering profession that goes with it. I recently rerolled JC and Inscription on my main with mining and herbalism on an alt. The crafting professions now give the better personal stat buffs since the herbalism "trinket" herbs will no longer be working after the patch. The possible exception to this view is enchanting, where you'll get the mats for levelling it as you level up.

In terms of healing priests the professions give you the following advantages

Skinning: 25 crit rating - minimal
Mining: health - minimal
Herbalism: lifeblood - minor self heal - meh
Enchanting: 38 spellpower from ring enchants - nice
Inscription: +37(I think) spellpower on shoulder enchant - nice
Alchemy: +37 Spellpower from flask (and double flask duration) - nice
Jewelcrafting: +3 High power prismatic gems (increased stat of your choice and activating meta gems much easier) - nice
Tailoring: cheap leg enchants, darkglow embroidery cloak enchant - nice
Engineering: Haste on glove enchant - I'd find it hard to justify for healing purposes, might have its uses.
Leatherworking: 37 spellpower on bracer enchant - nice, but you sure won't be wearing what you make
Blacksmithing: 2 colorless sockets that stack with other enchants - nice, but you sure won't be wearing what you make

At the end of the day you can take what you like, the crafting professions give similar buffs and the collecting ones give relatively minor buffs (but will likely make you more money)

I went tailoring/enchanting and think it is definitely the way to go for a priest. I do have a lot of other alts for gathering with mining or herbalism to make money but if you want to spend the time on the AH with Auctioneer you may do ok with DEing stuff. Though IMHO since others do it as well it is a pretty rare market on busy servers.

I've gone Tailoring/Inscrition personally and am very happy with the benefits I get out of these, the shoulder inscriptions are awesome and the cheap spellthread and cloak embroidery are quite a nice little buff too. Obviously I was able to fund the inscription from mains though or it would not have been so viable.