Here's a stab at some tweaks that I think would improve the Protection Tree and tanking for paladins:
In my opinion the need and effort involved in getting to an uncrushable state warps the class in many ways. For example, you simply cannot evaluate a lot of paladin tank gear as you would not wear it solely because of uncrushability.
We don't really know how a paladin raid tank would perform in true paladin tank gear. This is because if she was in true paladin tank gear, she would be crushable, and thus pointless. Similarly, a talent such as Redoubt is useless after uncrushability is achieved.
So I solve the problem Gordian-Knot-style, and simply fold uncrushability into Shield Specialization (additionally reduces chance of crushing blow by 5/10/15%).
Additionally, Blessing of Sanctuary is removed, and Kings moved into its position. With the smaller raid size, there are not really enough paladins to put all required blessings up, and Sanctuary is usually dropped. Kings is a good blessing, but not necessary in 10-man content, and only one paladin in 25-man content needs it.
I added a Fear Immunity, Blessing of Courage, into the 11-point slot, making it reasonably accessible to all specs. It's a short duration blessing, modelled after Blessing of Freedom.
The final change was to swap Weapon Expertise for a talent that returns mana when blocking. Because we are paladins, it is extended to return mana to the entire party. Seems in theme, but makes us different than warriors, as a paladin tank would more likely be put in a caster group.
We retain our strengths of being really good on fast attack or AoE fights, but we still have our weaknesses of lower health and damage mitigation than warriors.
We also get a lot more freedom to gear up. Basically, I'm tired of wearing warrior tanking gear, and would really like to wear paladin tanking gear.
Edit: Hmm. It appears that the talent tree site is down. Hopefully the description above is enough for people get the idea.