Diouf, a free agent after leaving Doncaster last season, upstaged Blackburn’s £8million buy Jordan Rhodes in a performance to undermine Rovers boss Steve Kean’s decision to release him 18 months ago.
Rovers had gone 2-0 ahead before the half-hour thanks to goals from Marcus Olsson and Nuno Gomes before Diouf struck on 41 minutes to get his side back on track.
Second-half goals from Ross McCormack and Luciano Becchio put the home side in front but when Morten Gamst Pedersen’s 84th-minute corner was headed into the danger zone, substitute Ruben Rochina pounced for an equaliser.
Diouf, who Warnock revealed has agreed a deal until January, should have won it for Leeds in added time but spooned his shot over.
The Leeds boss was nonetheless impressed with the performance of the Senegalese frontman, who drew the ire of the away support following his all-action display.
“I thought his contribution in the second half was good. He missed a good chance but they missed one a minute before,” Warnock said.
“The game was a good advert for the Championship but we were disappointed that the referee gave a free-kick against Tom Lees when Pedersen backed into him in the build-up to their third.
“Bill Shankly once said referees know the rules, they just don’t know the game.
“It was disappointing to be denied a win by a decision like that. I am so proud of my team for battling back from two down.”
Kean was also unhappy with referee Neil Swarbrick.
“It was a roller-coaster game and looking back we will think it was a decent point, but at two up we were in total control,” he said.
“We felt we were on the wrong end of refereeing decisions for two of the goals. The big turning point was when the referee didn’t give a foul on our keeper Paul Robinson, who couldn’t punch the ball with both hands and they scored their first goal.
“If we had gone in two goals up at half-time I think we would have won but full credit to Leeds. They had a real go. We have gone four league games unbeaten which is a solid start.”
Pedersen created the opening goal in the 19th minute for Olsson - his first since moving from Halmstads.
Eight minutes later the dynamic Pedersen linked up with Olsson who provided the pass for Gomes to fire past Paddy Kenny.
The tide turned when a corner was cleared only as far as David Norris. He returned the ball into the congested goalmouth where Robinson flapped at it and Diouf stabbed his first goal for Leeds, at the second attempt.
Leeds were level on 56 minutes, Rovers failing to cut out Adam Drury’s long ball, enabling McCormack to lash in a first-time effort.
Becchio nodded his side ahead after Rovers could not clear Diouf’s cross, only for Rochina to keep Rovers’ unbeaten league run intact.