The Protection tree is focused almost entirely on increasing your survivability, but it also has some usefully support and tanking abilities as well.
Improved Devotion Aura
Description:
Increases the armor bonus of your Devotion Aura by a percentage.
Ranks:
Rank 1- 8%
Rank 2- 16%
Rank 3- 24%
Rank 4- 32%
Rank 5- 40%
Usefulness:

Commentary:
This definitely deserves to be in the lowest tier. It has been buffed to give more armor but it is still not that great. There is no reason to put points in this unless your raid asks you.

Redoubt
Description:
Damaging Melee attacks against you have a ten percent chance of increasing your chance to block by a percentage
Ranks:
Rank 1- 6%
Rank 2- 12%
Rank 3- 18%
Rank 4- 24%
Rank 5- 30%
Usefulness:

Commentary:
This is an incredible ability for a first tier talent. Since it now procs off of any damaging attack it gives you more survivability when tanking multiple mobs. One of the core talents of the protection tree.

Precision
Description:
Increases your chance to hit with melee weapons and spells.
Ranks:
Rank 1- 1%
Rank 2- 2%
Rank 3- 3%
Usefulness:

Commentary:
Against an even level enemy you have a four percent chance of missing. So with these talents you will only miss once out of every one hundred swings. An all around good talent to get, especially if you are a tank.

Guardian’s Favor
Description:
Reduces the cooldown of your Blessing of Protection and increase the duration of your Blessing of Freedom.
Ranks:
Rank 1- Protection cooldown- 60 sec. Freedom duration- 2 sec.
Rank 2- Protection cooldown- 120 sec. Freedom duration- 4 sec.
Usefulness:

Commentary:
This is great, especially for a party and PVP environment. Cutting down on the cooldown of Protection means you can cast it nearly twice as many times. Increasing the duration of Freedom is also important in PVP where mobility is key.

Toughness
Description:
Increases your armor value from items by a percentage.
Ranks:
Rank 1- 2%
Rank 2- 4%
Rank 3- 6%
Rank 4- 8%
Rank 5- 10%
Usefulness:

Commentary:
This is ok, but really not that great since we aren’t as focused on damage mitigation as warriors unless we are tanking. I would wait and put points in it to gain access to tier 5 later on.

Blessing of Kings
Description:
Increases a target’s stats by 10% for 5 minutes.
Ranks:
Rank 1- One rank.
Usefulness:

Commentary:
Most raids have their paladins spec this far in the protection tree just so they have access to this. Since it is so well rounded nearly every class will benefit from it, definitely worth a point.

Improved Righteous Fury
Description:
Increases the amount of threat generated by your Righteous Fury spell by a percentage and decreases the amount of damage you take by a percentage.
Ranks:
Rank 1- 16% increased threat, 2% decreased damage.
Rank 2- 33% increased threat, 4% decreased damage.
Rank 3- 50% increased threat, 6% decreased damage.
Usefulness:

Commentary:

This talent has many different uses. It is primarily for tanks because of the increase to threat. In fact, it is absolutely necessary for a paladin tank. The damage mitigation aspect is also good as well. You can use it when soloing or in PVP where threat isn't an issue and stay alive longer.

Shield Specialization
Description:
Increases the damage absorbed by your shield.
Ranks:
Rank 1- 10%
Rank 2- 20%
Rank 3- 30%
Usefulness:

Commentary:
When I have to fight with a shield I find this incredibly useful. It's obviously good for tanks, but it is also useful for healers in case they pull aggro. Combined with Redoubt you will block attacks more often then most classes and take less damage because of it. Its situational though like most of the talents in the protection tree and limited to defensive fighting.

Anticipation
Description:
Increases your defense skill.
Ranks:
Rank 1- 4
Rank 2- 8
Rank 3- 12
Rank 4- 16
Rank 5- 20
Usefulness:

Commentary:
An extra ten defense are nice, but there are far to many other skills that are much better. It was recently buffed to make it more useful, but even then I would only put points in this if I need to fill points in to reach a new tier.

Stoicism
Description:
Increases your resistance to Stun effects by an additional percentage and reduces the chance your spells will be dispelled by an additional percentage.
Ranks:
Rank one- 5% stun resist, 15% dispel resist.
Rank two- 10% stun resist, 30% dispel resist.
Usefulness:

Commentary:
This is a somewhat average talent and there are enough better talents that will get you to the next tier. It would be very useful for tanking and some PVP situations but that is its main selling point.

Improved Hammer of Justice
Description:
Reduces the cooldown of Hammer of Justice.
Ranks:
Rank 1- 5 second reduction.
Rank 2- 10 second reduction.
Rank 3- 15 second reduction.
Usefulness:

Commentary:
Hammer of justice is one of my favorite abilities to keep targets from running away and by reducing the cooldown I found that I could use it almost every fight. It is a great talent for both PVE and PVP.

Improved Concentration Aura
Description:
Increases your concentration auras effect and reduces the duration of interrupt and silence effects by a percentage.
Ranks:
Rank 1- 5% extra chance to not lose casting time and 10% decrease for silence effects.
Rank 2- 10% extra chance to not lose casting time and 20% decrease for silence effects.
Rank 3- 15% extra chance to not lose casting time and 30% decrease for silence effects..
Usefulness:

Commentary:
Concentration Aura has become incredibly useful in PVP now that silence effects are no longer resisted and instead reduced. If your group is caster heavy you will almost always want to have the full three points in this. Even if you are the only caster you will still want to keep this available for yourself if you ever get silenced.

Spell Warding
Description:
Reduces all spell damage taken by a percentage
Ranks:
Rank one- 2% damage reduction
Rank two- 4% damage reduction.
Usefulness:

Commentary:

This is a very limited talent and only useful for those that intend to do nothing but tank. The reduction only applies to you now instead of your whole group so it's effectiveness is limited. It basically gives you some extra resistance to all schools of magic, but if you are going into magic heavy fights you should have resist gear anyway.

Blessing of Sanctuary
Description:
The targeted party member has all damage done to them reduced by 10. They also deal holy damage when they block an attack.
Ranks:
Rank 1- 10 damage reduction. 14 holy damage on block.
Rank 2- 14 damage reduction. 21 holy damage on block.
Rank 3- 19 damage reduction. 28 holy damage on block.
Rank 4- 24 damage reduction. 35 holy damage on block.
Rank 5- 80 damage reduction. 46 holy damage on block.
Usefulness:

Commentary:
This blessing is really only useful for a protection paladin. Other tanking classes would be better off with a different blessing. But it is one of the best blessings you yourself can use when tanking or AE grinding. The damage reduction is excelent, especially when fighting multiple mobs. And the extra holy damage means extra threat.

Reckoning
Description:
Gives you a chance after being hit by any damaging attack that the next 4 weapon swings within 8 seconds will generate an additional attack.
Ranks:
Rank 1- 2% chance.
Rank 2- 4% chance.
Rank 3- 6% chance.
Rank 4- 8% chance.
Rank 5- 10% chance.
Usefulness:

Commentary:
Reckoning was drastically changed in the 2.0.1 patch. Before, it would let you get an extra attack when you were hit with a critical strike. This was deemed as being overpowered because many people made it the central focus of their build. Now Reckoning is designed to be a piece of your play style and not the most important part. Before it was mostly only viable in PVP, now it is more balanced to go with any style of play. In PVP and solo it gives you some extra DPS which the Protection tree lacks, and it is great for tanking and keeping aggro. The extra swings will proc seals like Righteousness which means extra threat. And if you are AE grinding it means more damage to your current target.

Improved Divine Shield
Description:
Increases your stamina by a percent, reduces the cooldown of your Divine Shield spell and reduces the attack speed penalty by a percentage.
Ranks:
Rank one- Stamina increased by 3%, cooldown reduced by 30 seconds. Attack speed penalty reduced by 50%.
Rank two- Stamina increased by 6%, cooldown reduced by 1 minute. Attack speed penalty reduced by 100%.
Usefulness:

Commentary:
This talent has many uses. The increase to stamina is obviously best suited for tanks. The cool down and attack speed penalty reduction is also a boon for solo grinding and PVP.

One Handed Weapon Specialization
Description:
Increases the damage you deal with one handed weapons.
Ranks:
Rank 1- 1% increase.
Rank 2- 2% increase.
Rank 3- 3% increase.
Rank 4- 4% increase.
Rank 5- 5% increase.
Usefulness:

Commentary:
The whole point of the Protection tree is increasing your effectiveness with a shield, so its only natural that since you will be forced to use a one hand you should enhance that as well. Since one handers don’t deal a great amount of damage this is a welcome addition and increases Seal of Righteousness damage as well. When combined with the extra attacks of reckoning you will almost be dual wielding.

Improved Holy Shield
Description:
Increases damage by Holy Shield by a percent and increases the number of charges.
Ranks:
Rank 1- 10% damage increase, 2 extra charges.
Rank 2- 20% damage increase, 4 extra charges.
Usefulness:

Commentary:
This is primarily used for tanking where you need the holy damage for threat. Other than that it can be used for farming as protection spec. If you put points in this you will be able to take on more monsters at once.

Holy Shield
Description:
Increases your chance to block by 30% and deals damage with each attack blocked. Damaged caused by Holy Shield causes 35% additional threat. Lasts for four blocks.
Ranks:
Rank 1- 59 damage dealt on block.
Rank 2- 86 damage dealt on block.
Rank 3- 117 damage dealt on block.
Rank 4- 155 damage dealt on block.
Usefulness:

Commentary:
This is the ultimate Paladin tanking ability. Like Blessing of Sanctuary it decreases the damage you take and increases your threat. But it does a much much better job. It's greatest power is that it allows you to take on multiple mobs at once. If your block rate is high enough you will cause so much damage to a group of attacking enemies that your group mates will be able to AoE them down with no fear of pulling aggo. You will also need this if you intend to do AE farming.

Ardent Defender
Description:
When you have less than 35% health all damage you take is reduced by a percentage.
Ranks:
Rank one- 6%
Rank two- 12%
Rank three- 18%
Rank four- 24%
Rank five- 30%
Usefulness:

Commentary:
This is another talent that excels in increasing your survivability. Unlike Blessed Life the effect is predictable and will basically double the amount of time you have to pull off a saving heal. If your goal is ultimate survivability seriously consider this.

Weapon Expertise
Description:
Increases your expertise by a set amount and increases your total stamina.
Ranks:
Rank one- +1 expertise, +2% stamina
Rank two- +2 expertise, +4% stamina
Rank three- +3 expertise, +6% stamina
Rank four- +4 expertise, +8% stamina
Rank five- +5 expertise, +10% stamina
Usefulness:

Commentary:
This is another tanking talent. Expertise is designed to help you hit your opponent and reduces the chance that they will dodge or parry. Hitting is important for a tank to keep aggro and expertise gear is somewhat rare. The extra stamina is also incredible for increasing your survivability.

Avenger’s Shield
Name:
Avenger’s Shield
Description:
Hurls a holy shield at the enemy dealing holy damage, dazing them and then jumping to three nearby enemies.
Ranks:
Rank one- 270-330 holy damage.
Rank two- 370-452 holy damage.
Rank three- 581- 709 holy damage.
Usefulness:

Commentary:
This talent has many uses, the first and foremost being that it gives you a ranged attack. It is also great for tanking paladins since it gives you a burst of holy damage to gain agro. And finally it is good in PVP because it is able to stun several enemies at once. Its largest flaw is that it costs a great deal of mana and can’t be spammed. But if you have gone this far into Protection then you deserve to get this.