Besides a 2005 Ngati Awa settlement, and the Nga Kaihautu deal, signing off on settlements has been slow.
More than three attempts to build consensus across iwi and with the Crown have failed.
Dr Cullen said he wouldn't describe the amount spent as a "waste" because smaller settlements had been ticked off in the region.
He conceded that after millions spent and 17 years, both Maori and the Crown were "underdone".
"We haven't got a lot to show for it, because we haven't achieved success.
"We all recognise there's a bold attempt to get a broader settlement. It may or may not succeed.
"Nevertheless, I think it's worth trying again, I think there's a lot of good will to try and achieve that."
Paramount Tuwharetoa chief Tumu te Heuheu will lead the tribal initiative but other interesting features include using independent facilitators to negotiate. That process cuts across responsibilities usually handled for the Government by the Office of Treaty Settlement.
Dr Cullen would not accept that after a hammering from the Waitangi Tribunal this year in two reports the agency was effectively being given a time-out. He said OTS carried out most negotiations and continued to be important.
Facilitators had not yet been appointed but their presence would change the face of talks, he said.
"Iwi leaders, people who are elected sometimes feel that perhaps relatively junior [OTS] people are sent to negotiate. They feel like they want to be talking chief to chief."
Intractable tribalism remains the biggest threat to getting a result. Iwi will have to knock out a position among themselves where that's been impossible historically. Finding the balance between getting the best deal for each iwi while being pragmatic is the challenge, and it really will be a case of seeing past the trees to the forest.
"Difficult," is how Dr Cullen describes the attempt but if he can pull it off it will be a major coup for Labour and end what has been a contentious negotiating region which has seen multiple court actions and tribunal reports.
National's Treaty negotiations spokesman Chris Finlayson did not return phonecalls, but Dr Cullen's new role has some support.
Maori Party MP Te Ururoa Flavell said he welcomed the pairing of the Deputy Prime Minister and new Cabinet minister Shane Jones in the portfolio. Mr Jones had steered Maori through the fisheries allocation process. Other ministers had not worked with iwi before and instead left that role to bureaucrats, he said.
"He [Dr Cullen] is a big hitter in the role, with the support of Shane Jones - well, he comes with understanding about iwi politics."
TRY AND TRY AGAIN
* Ngati Tuwharetoa, Ngai Tuhoe and select Te Arawa iwi will negotiate to forge a settlement deal for the largest Crown-owned forest - Kaingaroa in the central North Island.
* Accumulated rentals for the forest total $202 million and is held by the Crown Forestry Rental Trust until iwi settle.
* Since 1990 numerous attempts have been made to find a broad settlement for iwi who have competing interests in the forest. All have failed.
* Nga Kaihautu o Te Arawa - a confederation which does not include all Te Arawa iwi - left the collective approach behind to push its own deal. Its 50,000ha, $36 million deal has been put on hold to see whether this latest collective grouping can achieve settlement. It has been assured any new developments must see it end up with a deal at least as good as the one that it has now.
* The 2005 Ngati Awa settlement is one success story in the region with $16.7 million in accumulated forestry rentals already transferred to the iwi.
