In other matches Friday, the Netherlands beat New Zealand 5-1 for its third win in a row; Germany moved to the top of its group with a 5-2 win over India; Britain beat Pakistan 4-1 on two goals by Ashley Jackson which brought his tournament total to four, and Spain beat South Africa 3-2.
Peillat said Argentina was finding its form.
"Our performance will give us a little bit more confidence, and that is a good thing for the two remaining matches that we have," Peillat said.
The goal was Dwyer's fourth of the tournament and his 180th for Australia, making him the all-time top scorer for his team, overtaking forward Mark Hager.
"It's a great honor," Dwyer said. "Mark Hager was a role model of mine."
New Zealand took an early lead over the Dutch on a fourth-minute field goal from forward Simon Child, who played his 170th game for his side. But goals from defender Mink van der Weerden and forwards Roderick Weusthof and Billy Bakker put the Netherlands 3-1 in front before halftime.
In the second half, Bakker added his second goal and midfielder Robbert Kemperman completed the Dutch scoring.
Britain dominated its crucial match with Pakistan which could determine Group A's two qualifying positions.
"Today was good fun ... we worked harder, and we worked harder for one another," Jackson said.
Pakistan captain Sohail Abbas scored from a penalty corner in the last minute of the game.
"Collectively and tactically they were better than us, so we have to work on that," Abbas said. "We would like the game to have been a bad dream."
Spain overcame South Africa to win their first game of the tournament. South Africa defender Justin Reid-Ross opened the scoring from a 26th-minute penalty corner, and Spain midfielder Marc Salles responded straight away, scoring from a Spanish penalty corner.
Spain added two more by Pau Quemada and Miguel Delas in the second half. South Africa came back into the game seven minutes before the end with a field goal by Lloyd Norris-Jones but couldn't follow up with an equalizer.