When it was announced that Orlando Bloom was to play Joe Byrne I thought it was a bad discussion (I still do). There was a sci-fi forum that I belonged to which had a forum just for Orlando Bloom. I made the mistake of commenting soon after his role was annoucned (and before filmimg had started) that I thought that Orlando Bloom would make a better Steve Hart than a Joe Byrne. All hell broke loose as little fan girls thought I was belittling the precious Orlando. These were girls who knew nothing about the Kelly legend and, even though I tried to explain my reasons, the admin decided it was better to ban me for being a troll.
You don't cast an actor purely on how much they look like the charachter.. Ledger is a far better actor...btw Bloom looks nothing like Ned Kelly, at all.