At Bruce Pulman Park in Takanini, Auckland, the Wanganui team had a great start, beating 2013 finalists Bay of Plenty then accounting for Manawatu, Counties Manukau and Horowhenua.
Next day they defeated reigning champions Auckland, then drew with Wellington and lost to North Harbour before beating Otago in the last pool match.
Millar said due to a couple of injuries, they played the North Harbour and Otago matches with only eight players, resting two.
Teams could take up to 16 players to the nationals, but due to last minute withdrawals they had been reduced to 10.
Tied on points with North Harbour, Wanganui beat them to make the final.
However, Auckland won the last match to retain the championship, which they have dominated in the Over 40s grade for the past decade.