You ever thought "I need to do a post about X", and then open up your FeedReaderOfChoice and someone, much smarter than you, has just done a post about X?
Well in this particular case, X happens to be Professions. And the person much smarter than I is none other than Shia at Banana Shoulders.
In this excellent post, she breaks down the Professions with the benefits they provide to the Crafter herself.
What I'd like to do is analyze each professions benefits from the standpoint of a Protection spec Paladin. There are more benefits to the profession than what I list. See Shia's post for a comprehensive list.
Blacksmithing - up to 3 additional sockets, 'Blue' BoP gear.
The sockets don't overwrite enchants so you can still enchant and socket your gear. These are more opportunities to add Defense or Stamina to your gear kit.
Jewelcrafting - Better and colorless Gems, can only use 3 at a time. BoP Trinkets (which are likely to be replaced with Raid Drops)
The gems will help you get a socket bonus that you might not otherwise get, and they are better than any other gem you can get for a slot.
Enchanting - Ring Enchants.
These are the only way to get the Ring enchants. and they have one for Stamina.
Leatherworking - LW only Stamina and Resist enchants
If you've done much tanking tBC, you know the 'joy' of putting together a resist set. The stamina on the enchants is better than the stamina you can get from the enchant Enchanters have.
Inscription - Better Shoulder enchants
The shoulder enchants are nice, but I feel like you get more from the Strong Choices
Mining - 500 Max Health
More health is always good as a tank, but it's health not Stamina so it doesn't scale.
Alchemy - Better effects from your Flasks and Elixirs and a BoP Alchemist's Stone that gives Stam and Dodge (which is likely to be replaced with Raid Drops).
You elixirs are 50% more effective for you. In tBC terms that means a 500hp fort Elixir becomes 750. Nice, but not that huge.
Engineering - Nitro Boots, BoP Goggles (which are likely to be replaced with Raid Drops)
The nitro boots can give you the mobility the Protection Paladin lacks at the moment. Nice, but again not that huge. I have loved my Goggles for most of tBC and they lasted me until I got my Tier 6 hat. It looks like the new Goggles will be replaced in Tier 7 (first Raids).
Tailoring - BoP mount, Self Only Spell Threads, Self Only Cloak proc Enchants
The flying carpet is cool but ultimately has no bearing on you as a Protection Paladin. I don't like procs so I certainly won't take a profession whose main perk for me would say "has a chance to...."
Herbalism - a weak HoT
This could be nice since our ability to slam Health pots is reduced in the expansion, but ultimately it's too weak, and if it has a cast time, we can't cast it while tanking.
Skinning - Crit
Even moving to a Warrior type of tanking, Crit is still not a strong threat stat.
So what do you recommend, Honors?
It looks like Jewelcrafting and Blacksmithing would be a very strong combination for a tank. Personally, I'm going to keep Engineering and Jewelcrafting. I dropped Engineering at the beginning of tBC and I ended up regretting it to the point of relearning it. I'm going to wait until around Level 75 and then reevaluate if I want to keep Engineering.