Certainly moving to a return basis makes sense so that miners pay more when resource prices are high and less when they are low. And using a bond rate is reasonable as any return above this comes from mining the resources.
If you accept the above as being true, the issue then becomes the rate at which the tax is applied. This needs to take into account a fair return for Australia of using its resources, but also consider significant competitors if the tax is applied at such a rate as to significantly reduce mining investment in Australia. Obviously, it will stop investment in marginal mines.
Personally, I think the rate is a bit high, but overall idea is a good one.
