Tank Paladin Spec
The objective here is to keep aggro focused on the Paladin. The main objectives are Spiritual Focus, Illumination and Divine Favor in the Holy tree, Blessing of Sanctuary and Improved Seal of Fury in the Protection tree, Vengeance and Consecration in the Retribution tree.
Holy Talents (14 points)
Spiritual Focus - 5/5 points
Gives your Flash of Light and Holy Light spells a 70% chance to not lose casting time when you take damage. This is a required ability for a Paladin IMO. Healing in combat adds to your aggro.
Improved Holy Light - 3/3 points
Increases the amount healed by your Holy Light spell by 12%. Holy Light is the healing spell, 12% more is good.
Revelation - 2/2 points
Reduces the cooldown of your Lay on Hands and Divine Intervention spells by 20 minutes. This just sounds great.
Illumination - 3/5 points
After getting a critical effect from your Flash of Light or Holy Light spell, gives you a 60%? chance to gain Mana equal to the base cost of the spell. Free mana for a Heal is great.
Divine Favor - 1/1 point
When activated, gives your next Flash of Light or Holy Light spell a 100% critical effect chance. Now I get to pick when to have a double strength free heal. The only way it could be better is if the heal was instant.
Protection Talents (16 points)
Redoubt - 5/5 points
Increases your chance to block attacks with your shield by 30% after being the victim of a critical strike. Lasts 10 seconds or 5 blocks. While tanking I'll need defense.
Improved Devotion Aura - 5/5 points
Increases the armor bonus of your Devotion Aura by 25%. Need to get up the tree. Helping the rest of the party seems a decent way to do it. I didn't take toughness due to the cap on total armor at 7000.
Improved Seal of Fury - 5/5 points
Increases the amount of threat generated by your Seal of Fury and Judgement of Fury by 15%. I said I wanted aggro, didn't I?
Blessing of Sanctuary - 1/1 point
Places a Blessing on the friendly target, reducing damage dealt from all sources by 7 for 5 minutes. Players may only have one Blessing on them per Paladin at any one time. More tanking goodness. Stack this with the Warlock debuff, 7000 armor, and Redoubt and we'll see what we have.
Retribution Talents (21 points)
Improved Blessing of Might - 5/5 points
Increases the Attack Power bonus of your Blessing of Might by 20%. Helps the whole party do damage.
Improved Seal of the Crusader - 5/5 points
Increases the Attack Power bonus of your Seal of the Crusader and the Holy damage increase of your Judgement of the Crusader by 15%. Gets me up the tree.
Vengeance - 5/5 points
Gives you a 15% bonus to Physical and Holy damage you deal for 8 seconds after dealing a critical strike. Additional damage will help hold aggro. Gets me up the tree.
Seal of Command - 1/1 point
Fills the Paladin with the spirit of command for 30 seconds, giving the Paladin a chance to deal additional Holy damage equal to the damage of the Paladin's weapon. Only one Seal can be active on the Paladin at any one time.
Unleashing this Seal's energy will judge an enemy for 30 seconds, causing 24 Holy damage any time the enemy becomes stunned. Only one Judgement per Paladin can be active at any one time. This looks like it combines well with Vengeance for just one point.
Deflection - 4/5 points
Increases your Parry chance by 4%. More defense for tanking. Gets me up the tree.
Consecration - 1/1 point
Consecrates the land beneath the Paladin, doing 120 Holy damage over 8 seconds to enemies who enter the area. This is my main way to grab aggro in a multi-pull.
Commentary
I like the Retribution tree but if I want to do massive damage I can play a Rogue. The Protection tree above Imp Seal of Fury are underwhelming. There are a few more Talents in the Holy tree that I'd like but if I wanted to heal I'd play a Priest or Druid. I like the fact that I can do secondary healing and I'd like to see what kind of melee damage I can do.
It is interesting to see that I ended up with the most points in the Retribution tree as a Tank specced Paladin.
If I was willing to give up Consecration I would take points out of Deflection and Consecration and put them in Illumination and Imp Flash of Light. If this didn't affect my ability to hold aggro too much I would gladly become a better healer.
Alternatively Holy Shield may prove to be the killer Paladin tanking talent in which case the Three Tree Build may be the better way to go.