This entry contains spoilers
WTF? Is this the best idea that 3 people come up with, "Let Matt Parkman make Sylar believe he is Nathan Petrelli!". Wow!
Do you remember Season 2 Episode 9, Cautionary Tales? Noah was shot dead by Suresh:

But then they resurrected him with the Claire's blood.
OK. Let's say "resurrection technology" is not applicable for Nathan. Why did they needed Noah? Quoting from Angela Petrelli:
- Who will convince the president that the whole thing was a mistake? Without Nathan, nothing is going to change.
Well, OK, assume that president will only believe in Nathan. Two spontaneous thoughts on how to accomplish that:
- Let Peter shape-shift into Nathan.
- Let Parkman convince the president.
I guess I understand producers' concerns. Heroes wouldn't be complete without Sylar. Killing him would make lots sad. But couldn't they think of a script that would make him just fail, probably with losing some of his abilities?
Heroes Volume 1 was great. Volume 2 was doing well until writers' strike. Volume 3 was tremendously bad. I gave Volume 4 another shot, and it was going on a very thin line between fun and absurdity. My hopes for Volume 5 are very low.