The latest patch notes have the following:
- Sacred Shield: The damage absorption effect from this ability now triggers only once every 30 seconds.
- Infusion of Light: This talent now also reduces the cooldown on the effect of Sacred Shield by 12/24 seconds.
This is Blizzard saying that Sacred Shield really should have been a deep Holy talent, not something available to all paladins. However, they probably don't want to mess with the structure of the trees when Cataclysm is going to change them anyways. So the change effectively makes Sacred Shield a Holy-only spell.
I think the real, underlying strain on paladin design is Touched By the Light and Sheath of Light. I confess that I really liked these talents, as they were an attempt to retain some of the fluid hybrid nature of the original paladin.
But perhaps that goal just isn't worth the problems it causes. If Touched by the Light and Sheath of Light did not exist, maybe paladin design would be stronger. Prot and Holy would still have access to heals and Sacred Shield, but they would be much weaker, only using the base values for those spells. Blizzard wouldn't have to be doing these shenanigans to keep these hybrid specs in check.
If those two talents were gone, AP and SP coefficients would also be de-linked, and could be tweaked independently of each other, so Holy could be strengthened or weakened independently. Of course, it's too much to do now for 3.3 as you'd have to tweak almost all AP coefficients.
Perhaps the best way to retain "hybridity" for paladins would be to be specific, rather than general. For example, supposed Art of War gave you an instant Holy Light instead of Flash of Light. Sounds overpowered, but without Sheath of Light a Ret paladin would have zero spellpower, so that HL would only hit for the base heal.
This way the hybrid nature can be carefully controlled, and specific instances can be changed. A general solution only seems to result in general nerfs.