Tanking and Holy Spec

Hey!
I've been playing in Nostralrius for a quite while, changing between Horde and Alliance, changing between the classes until realized to finally return to Paladin which is still the class I love playing with.
While quick search didn't give me really results, I wanted to hear bit opinions how likely it's possible to tank some late game dungeons (not raids, duh) with deep Holy spec, going to deep as getting a Holy Shock. And can be build be made with such spec reasonably.
I personally enjoy a lot playing both Healer and Tank but my mood about which role I wish to play changes really often so I wanted to hear if that's fully possible idea.
I've been playing in Nostralrius for a quite while, changing between Horde and Alliance, changing between the classes until realized to finally return to Paladin which is still the class I love playing with.

While quick search didn't give me really results, I wanted to hear bit opinions how likely it's possible to tank some late game dungeons (not raids, duh) with deep Holy spec, going to deep as getting a Holy Shock. And can be build be made with such spec reasonably.
I personally enjoy a lot playing both Healer and Tank but my mood about which role I wish to play changes really often so I wanted to hear if that's fully possible idea.