heroes - Why were Hiro’s powers so sporadic?

The show Heroes was originally written as a one season series so a lot of the stories and characters were were not thought out in a way that would lead to more development. The second season of Heroes was affected by the writers strike. Story lines were dropped in the middle of development and writers were changed. It caused a lot of inconsistent plots and resolutions. It was shown that in season one that his own confidence in his abilities seemed to affect them. When he was in Vegas he seemed to lose his powers because he had lost confidence in his ability due to the killing of Charlie the waitress and his inability to stop or change the outcome. He later seems to master or at least have control over his powers as well as the ability to use a katana by the end of Season one.

It’s also shown in Season One that in the future he masters the English language and also has gone years without letting anyone know he could time-travel as well as teleport. In later seasons Hiro seems to lose his powers for reasons that aren’t always given. When thrown back in time to Japan he can’t get back to his own time. Later on he is reduced to the mental state of a child and given a brain tumor which is killing him.

The real reason this happens is inconsistent writing. Also Hiro and Peter both had extremely strong powers. They both could of potentially solved any conflict with their powers. So the writers had to start writing weaknesses that they didn't have before. Peter was only able to keep one power at a time. Hiro's ability to use his powers become more sporadic.

The cannon reason as far as Season one goes is that Hiro's power is one of the greater ones and much harder to control properly. The easiest for him to do is teleport and stop time. Using time travel effectively seems to be the hardest. Future Hiro has an extensive 3-D time chart that he has used to figure out exactly how to change the future for the better. So even with mastery of his powers he is struggling to try to change time. The only way he can do it is to time stop Peter on the subway and give him a vague message "Save the Cheerleader, save the world". Also it seems that the further back in time Hiro goes the longer it takes him to use his powers again almost like they need to recharge.