At the same time though, a Paladin tank is constantly regaining mana (if they are doing things right :P), so there is no need to increase our mana pool at all. While leveling up, it's no big deal, and you may find having some extra intellect to be worthwhile when soloing. But, having intellect on your gear while in any type of group setting is completely irrelevant.
Same with agility to a certain degree. If you get gear that happens to have agility on it, as long as its other stats make it an upgrade, then cool. But, don't actively seek out agility. Other stats are far more important.
I disagree somewhat on what arthoriuss said in regard to stats. Defense is your first priority: 540 minimum. Then it's situational which stats will give the best results, not a cut and dry stamina > avoidance. Some fights your avoidance will help you very little, so a high health pool is the better way to go. Others, avoiding as much as you can will help you live longer than a very high health pool. Some situations block with a high block value means a lot, others it means very little. 2 ways you can prepare for this:
1) keep a few spare pieces of gear to change depending on the mechanics of a fight. I have my normal tanking set up, then I have a "block kit" mostly for trash or add tanking, and I have an "avoidance kit" for bosses like Patchwerk.
2) if you don't want all that gear, just try to keep a good balance of stamina and avoidance at all times. Reach for the 102.4% block cap while getting as much stamina as you can.
Don't go for one so much that you ignore the other, but balance the 2.
I also would say strength > block value. Strength adds BV and AP, so with strength you are not only upping your mitigation through blocking and threat from Shield of Righteousness, but increasing threat from melee and everything else that scales with your AP. Thankfully though you won't have to worry about choosing one over the other much of the time.
Gems: I use
Solid Sky Sapphire for blue sockets,
Enduring Forest Emerald for yellow sockets, and
Regal Twilight Opal for red sockets, or like my gear is now when I have no red sockets but need a red to activate a meta. You should also consider
Thick Autumn's Glow for trying to get to defense cap.
For meta I go with
Austere Earthsiege Diamond, though you could argue that the
Eternal one is better, particularly if you are not yet at the defense cap, or having trouble staying there.