Dentist is on the list of skilled occuptions. Therefore, the job itself qualifies for points as long as you meet the criteria (Bachelor degree or 5 year's work experience).Dentists also require occupational registration from the New Zealand Dental Council.
Your Australian work experience will likely be easily accepted as long as you have work references and tax records.
I suggest that the first priority should be dental council registration and then finding a potential job offer. You should also calculate your EOI points to make sure you will be eligible. Depending on your circumstances you may need to have a job offer outside Auckland.
The long term skill shortage list is actually mostly irrelevant for residence applications. Some people can claim bonus points if they meet the strict criteria, however in my experience it is not usually required. If an application does meet the long term skill shortage list requirements then that person may be eligible for a "work to residence" visa, bit this pathway takes over 2 years to result in residency. If you are eligible under the Skilled Migrant Category then don't worry too much about whether your job is on the long term skill shortage list.
Yes, getting a job offer is important, but you should also be aware of the dentist registration requirements for residency. Good luck with your job search.
David Fisher, LLB
Www.capitalimmigrationservices.co.nz