Jose Peseiro's men took a seventh-minute lead through Mohamed Al Shehhi, and that advantage was doubled just after the hour-mark courtesy of Damian Diaz's strike.
Mohamed Ismail was shown a second yellow card deep into stoppage time to compound Dubai's misery.
The win ensured the hosts are now on 45 points, and with one game remaining it is all to play for in the battle for the last two Champions League berths.
With runaway champions Al Ahli having secured their place weeks ago, there are three points separating five sides from third to seventh heading into the final round of fixtures.
Included in that bunch of teams are Al Shabab and Al Jazira, who both dropped points from their respective away fixtures.
The former went down 3-2 at Emirates, who were thankful to Rodrigo Souza's brace after goals from Nasser Masood and Adeilson had twice pulled the visitors level.
Al Jazira drew 2-2 at fellow Champions League contenders Al Ain, for whom Asamoah Gyan scored twice in the first half to put the hosts 2-0 ahead.
The away side fought back in the second half, Felipe Caicedo pulling one back in the 68th minute before Al Ain had Fawzi Fayez dismissed and Ali Ahmed Mabkhout equalised nine minutes from time.
Al Ain sit sixth, level on 40 points with Al Sharjah, who were held 1-1 at bottom side Al Shaab.
Ahmed Jumaa gave the home side the lead after 18 minutes and although Ahmed Khamis levelled matters 11 minutes later, Al Sharjah could not force the winner that would have seen them gain ground on their rivals.
The other side in the mix for a Champions League spot, Al Nasr, won 2-1 at home to Al Dhafra thanks to an 89th-minute winner from Mahmoud Kamis.
Elsewhere, Al Ahli came from behind to beat Ajman 2-1, while Al Wasl's 2-0 win at Bani Yas was their first in the league since late January.
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