You're basically saying what I'm saying:
Disc is viable, but not as strong as holy on Nefarian 10man. Power Word: Barrier is the only thing keeping Disc viable for that encounter unless you can chain PW:B with other similar cooldowns so that you most of the time are taking the edge off the Electrocutes. Yes, they do bring different strengths. But aside of PW:B, i don't see how I am going to be able to do a better job on my raid than running holy.
Don't misunderstand me, i think Disc is a lot of fun. But i don't want to gimp my raid even slightly just because I like Disc better than Holy or think it's more fun to heal as a Disc priest (such as the smite-spam spec in the video for instance; He's having the other two healers cover for his selfishness).
It's also a bit contradictory; In the first example of a disc priest on nef 10 he was smiting and having the others pull his weight a bit.
The second one was Raidhealing, however in p2 the poor restoration shaman had to cover 3 people whilst the Disc priest only did 2. The raidhealer is covering less people in p2 than the tank one? Makes absolutely no sense aside from proving my point that Disc only is brought for PW:Bs and _mainly_ because the pries player prefers Disc.