It is possible to achieve (WoW Gold)very good retribution gear regardless of professions, however, from personal experience there's a few professions that really stand out:

1. Blacksmithing: As previously mentioned(Cheap WoW Gold), the Weaponsmith 2h weapons and their upgrades are excellent, attainable weapons for Retribution Paladins. There are good alternatives from Arena and Instances, however if you're aiming for the best there is, Macesmith is the way to go. This profession can go a long way, for example: The Tier 3 macesmith weapon (Stormherald) is the 2nd best weapon for Retribution Paladins that currently exists in WoW itemization (No.1 being Torch of the Damned, from deep in the Black Temple).

2. Alchemy: Besides making it easier to make pots, elixirs and flasks, the main reason why I highly recommend this is the epic Alchemist's Stone trinket. It gives you +15 to all stats, which is perfectly suited for a retribution paladin as well as an equip bonus that gives you 40% more from any mana/health potions you use. This bonus is highly recommended in PvE.

3. There are other benefits to be gained from other professions, like Engineering (Grenades/Trinkets), Enchanting (Ring enchants 2x+4 to all stats), Jewelcrafting (personal epic gems next patch), so no choice is necessarily wrong. 

Actually the link you yourself quoted says 5% Melee Hit Max% against level 70 (PvP) and 8.6% Melee Hit Max% against level 73 (PvE bosses/raiding), so I don't know where you're getting your numbers from? Maybe you misread the Spell Hit as Melee Hit? /confused Get naked, look at your crit %, it should be 3.93% (8.93% with talents), put on a piece that has just agility (but no crit rating), take note of crit % increas. Divide Amount of agility that you increased by, by the crit % increase. For example, I have 8.93% naked, adda ring with 12 agility, increases crit to 9.41%, thats a 0.48% increase, so 12 / 0.48 = 25.

Also, yoiu will see that the agility on your(Cheap WoW Gold) character tooltip says adds 3.73% crit, but your crit % (in my case) is 3.93%, thats because I have a sword equipped and because my weapon skill is 355, I get an additional 0.20% to crit.