Now I have to say Lost probably had it right by structuring it so that they had plenty of interesting material to carry them all the way until the end. Heroes has simply been struggling to find out what it wants to do.
What kills me is that
Lost is so much harder of a concept for writers to pull off. What the frak is it about? It's really about the characters, which means those characters must be great - there's no hiding bad characters with plotline gimmickry. How do you corral all these characters into one coherent story? How do you pace the story so the audience doesn't give up in frustration while the story spirals out of control or gets hopelessly bogged down? How do you keep it from being repetitive, and give each season a unique feel without it all seeming disjointed? It's impressive that they pulled it off at all, much less so well.
Heroes is easy! It's the
X-Men without costumes. The theme is that super-powered people will always be outsiders and looked upon with hatred and fear, and to some extent, this is even understandable, because mere humans cannot be expected to use the powers of gods wisely. But these people have powers, cannot figure out how to get rid of them easily, and in many cases, see their powers as part of their identity and don't want to get rid of them.
Each of the characters have an arc that leads to one of three destinations: their powers destroy them; they give up their powers, realizing they cannot control them; or (and this should be limited to one character, perhaps this is the role that can give Hiro purpose) they manage to defy the odds and learn to use (or not use) their powers with wisdom. Hiro wanted to be a Jedi, and a Jedi someone with a godlike restraint and wisdom to know when
not to use power.
Just follow that template and craft interesting plotlines around it. Don't worry about shoehorning the characters together into a "team" till it feels natural - and given their mutual predicament, it
will feel natural around S3 or so. Put them through trials that convince them that while other supers can be their greatest enemies, they also can be their only friends. They should have been able to get six or so very good seasons out of that setup.