If AKL don't check you in, when you get to DOH head to the transit desks in the transfer security area. They can issue your BP and you can ask them there if they can retag your bag (you will need the bag receipt given to you at AKL). The handling system will know where it is as it gets scanned multiple times as it passes through the system. Assuming they say yes, someone will pick it up (possibly even from the belt as that may be the easiest place), change the tag and send it on its way. Be sure to ask them if it will be travelling under the same bag receipt number or if you need a new one, in case of any problems later.

This doesn't work if the time between flights is short, say 90 mins, but 8 hours is plenty.

I have also been able to ask them to retag a bag in AS before but that was when a rolling delay began to create problems for going landside during a change at my next airport. But you can certainly ask at the service desk in the lounge to check all is well with the redirection a few hours later to put your mind at rest.