This is a good post. I have only a few comments to make in response.
Mitigation: I don't have much to say here, as Blizzard is still tuning defensive stats across the board.
Reckoning: I agree this talent needs a change. If it's intended for PvP, then, well, how many Protection Paladins do you see running around in Arenas? Maybe it should go down to 1 or 2 talent points, or have some additional effect, as suggested by Lore.
Taunting: RD was really cool when it was introduced. Where the Paladin is the MT, it's very powerful. But in a chaotic situation it sucks balls when you miss your taunt because the mob changed targets too quickly or you accidentally pull stuff off the other tanks. Maybe it should be changed so that if your target is hostile, it taunts that target, but if your target is friendly, it acts as it does now...?
Righteous Fury: I'm not sure I agree with this - sure it's an odd duck spell but its benefit is really high. The dispelling issue is the one major problem; if it could be made undispellable (maybe through talents?) it would make those fights much more survivable.
Blessings: The major issue here seems to be that Protection Paladins are being encouraged to spec for both Kings and Sanctuary, when both of these buffs are extremely desirable for tanking (and have no synergistic equivalent from other classes). Everybody is going to want Kings, so the question is: which Paladin provides it? I kind of like the idea of making Mark of the Wild equivalent to Kings, but you'd have to either take away the resistance and armor buffs from MotW or give them to Kings to have the two spells properly synergize.
Not Tanking: Honestly, having the Tankadin fill a healing role when not tanking makes more sense from a class design perspective than to have it be a subpar DPS. In either case, though, you have the critical problem of mana regeneration, something Warriors, Druids, and Death Knights don't have to deal with. If a Tankadin throws on healing gear for certain fights, though, he can be very effective at that role, especially since his gear will support crit heals, which synergize well with that talent bonus. The bonus to spellpower will also significantly improve his DPS if he should choose that role.