QFF Classic Rewards: Why is the multi-leg trip price so much more than the individual legs?

I’ve searched and found the flights I want to book with Classic Rewards and the taxes, fees and charges as below:
Auckland-Kuala Lumpur $63.35
Kuala Lumpur-London $93.20
London-Dublin $77.49
Dublin-London-New York $316

Per the individual searches the total comes to $627.53. However, when I try and put these into the multi-city it comes out at AUD999.79 for the same flights on the same dates/times.

The only thing I can think of is when I search individually I’m taken to the departure country’s webpage and the fees are calculated in the local currency, however when I do the multi-search it calculates in NZD (the country of first departure). This is a large discrepancy however, is there anything I’m doing wrong or can do to avoid this?

Carrier surcharges vary depending on the country where the ticket originates from. There is no way around it unless you book the flights as separate tickets or start collecting points in a different frequent flyer program which does not pass on surcharges to the customer.