I seem to be in a minority on this, but I can't see any point in the video ref rule at all. What does it actually achieve? If anything, I think it's worse than the system we already have. With the old system, sending a decision to the video ref was a tacit admission by the referee that he didn't see what happened. As such, I think there was a built in deterrent (albeit a mild one) to going to the screen all the time - a referee who goes the screen for everything would basically be admitting that he doesn't know what he's doing.
The NRL system, on the other hand, gives the illusion that the referee is making a decision (let's face it, it is only an illusion - only in 'benefit of the doubt' situations does it carry any actual weight). But because the referee is seen to be making a decision then there is no 'shame' in going to the video ref (rather than it being an admission of ignorance, it's more like saying 'I did see it, and I know what I think, but I wouldn't mind a second opinion'). The result, if my experience of watching the NRL tells me anything, is that referees go to the video ref for pretty much every single try.