BTW, Hiro is back about 6 months, remember? That's when everyone started getting their powers. Hummmmm.....
Coincidence or not?
Now ponder this:
Future Hiro told Peter he had to save the cheerleader, and Hiro had nothing to do with saving her since he went back in time to save someone else. Now, does Future Hiro mean he, himself, has to save her later at another point, or did he mess something up in time/space relations? Why did the clock in the diner click backwards one second?
Peter had to save Claire because he's the only one that could survive a Sylar attack, since he takes on the powers of others.
The painting has Peter with a scar on his face, but the scar healed with Clair around.
There's also blood on the Homecoming sign in the painting along with Hiro and Ando.
So maybe Hiro saves the waitress, alters time again, saves the cheerleader, but Sylar escapes.
Stopping Sylar won't stop the bomb, and stopping the bomb doesn't Save The World.
This is set up to replay with different outcomes for a long time.
One last thing, are you sure they saved the right cheerleader? She doesn't look like the one in the painting with the blood all over her. Jackie died.