His Te Puna teammate Terrence Hepetema, who has played for the New South Wales Warratahs and Leicester Tigers in England, was also in the Wasps starting lineup.
The fourth try of the half was from Rotoiti's Zak Hohneck.
Tauranga's Nick Evemy converted three of the four touchdowns in the half.
With both coaches making wholesale changes at half-time, Cavaliers found more steel in defence and scored 19 points without reply.
McMillan said the pattern of the game reflected the changes made.
"We probably had a little bit more experience on the field in the first half and that was probably reflected in a slightly more dominant performance, whereas they had their experience on in the second half and that's probably why they played a lot better."
After a trial game in Rotorua, McMillan said the Wasps v Cavaliers game served its purpose.
"There were some things from a team performance that we wanted to see improvements in from the trial, but we've got to be realistic about that too because they've only had one training together.
"Some of our younger guys probably also learned a few things about what it's like to play at the next level."
He said the first half defensive attitude was probably the most pleasing aspect of the game. "We put in some good tackles, there was a lot of resolve there, and a lot of pride in our line, so for me that was probably the most positive thing."
McMillan has taken a lot from the trial and the Wasps game. "I think we're tracking really well. We're really happy with where the strength and conditioning are at.
"The attitude has been really great, the guys are really committed and understand that at some point they need to make some mental shifts and when that happens we are going to get better results - so from that perspective I'm really happy with the way we're tracking.
"That's all going to help when we start to solidify the group and get together full time. I'm certainly optimistic we will have a much better season."
The Steamers team will be named ahead of two ITM Cup pre-season matches against Auckland on July 31 in Whakatane, and Manawatu on August 6 in Tauranga.