On-loan Blackpool striker Euell, who scored the first goal by a Rovers player at the Keepmoat Stadium since January 22, cancelled out Danny Graham’s 17th league goal of the season.
John Eustace was sent off 10 minutes from the end, after collecting a second yellow card, But both sides lacked a cutting edge to claim victory.
The draw dents Watford’s play-off push while Rovers are still without a win in six league games as they look to move clear of the npower Championship relegation zone.
The Hornets broke the deadlock after 22 minutes when Andreas Weimann cut the ball back towards Graham, who headed in from close range.
Rovers equalised on the stroke of half-time when Hird sent Euell through and he fired a shot past the keeper, with the ball hitting both posts before crossing the line.
The Hornets were reduced to 10 men with 10 minutes remaining when Eustace, who was booked in the first half, was shown his second yellow card for a deliberate handball.
Doncaster manager Sean O’Driscoll said: “The goal we conceded was poor from our point of view but I thought both teams were always vulnerable to being beaten by one ball over the top.
“I thought we had the better chances to win the game, especially in the second half, but when you lack quality you have to be competitive and at least we had that.”