Olver had several roles in the story so far:

- He was there for Mat to take responsability and grow up, because Olver depends on him. Mat can't be a child anymore except in his heart: he's a man now. As a counterpart, it's up to adult to make sure Olver has as much of a childhood as possible. He can't be a man at 10 y.o.

- Olver is also a mirror of what Mat used to be, almost to the point of caricature. He was an opportunity to keep Mat's childish side, and the humour surrounding it, into the series while making Mat himself mature.

- A child character, especially an orphan, always works well as a victim of war and chaos, as well as an example of human resilience.

- Olver was the plot device RJ needed to make Mat remain in Ebou Dar.

- Olver was the plot device to keep the game of Snakes and Foxes more directly in the series. "eh... remember playing S & F when you were a kid?" works only so many times. RJ needed a better way to have the game present and have a believable audience for Birgitte's stories about S & F, and Olver provided all that.

So Olver was far from useless as a character, and the series isn't over yet and there may well be more to come. Mat has to realise at some point Olver isn't emulating "his uncles", he's emulating him and it's his responsability to be a proper role model for Olver. As idolatry/hero worship goes, Olver is sort of a pendant of Aram in Mat's story line. It ended very badly for Perrin, but I get the feeling it will end well for Olver. But Mat will have to put his foot down as an authority figure at some point, or Olver will follow "his hero" blindly into danger, or do something really stupid to emulate Mat.