As for HEROES, yes, the Miya storyline was a bust from the get-go, and creator-producer-writer Tim Kring has said as much. I suspect we'll be seeing the last of her soon.
I disagree firmly about the character of Sylar. I find him dangerous and creepy even when he has little to do. He's a psychopath and just his presence for me adds a danger and a tension to a scene knowing that he's capable of any atrocity.