The win looked to be theirs when Jason St Juste scored a third to cap off a long solo run, but Rovers shrugged off their earlier defensive outlook to record their 20th draw of the season.
Darlington's push for four wins in a row had ended in a home defeat to struggling Kidderminster two days earlier but they wasted no time in getting their promotion hopes back on track.
With just one minute gone Craig Russell drove a low shot wide of Ryan Clarke's outstretched left hand.
Craig Russell had rounded off a slick move involving Chris Hughes on the right flank which had seen left-back Robbie Ryan hopelessly stranded between them.
For the rest of the half the question was when Darlington would score again but after three minutes of added on time it was Rovers who walked off with an equaliser to inspire manager Ian Atkins' half-time team talk.
Time had been added on after one of the referee's assistants had pulled a hamstring and Ryan turned the half around with a hectic charge through the middle.
Darlington's midfield, which had been so in control until then, was shocked by the pace of it all and after riding three tackles Ryan released the ball to Junior Agogo and a quick ball in to Richard Walker saw a rising shot swept in.
Darlington were left regretting chances missed by Craig Hignett and Craig Russell but four minutes after the break they were back in front.
St Juste went down under a challenge from Aaron Lescott on the edge of the box and home protests were waived away before Hignett slid the penalty into the unguarded section of the goal.
And when St Juste started a marvellous run from the halfway line to the edge of the box before finishing with a devastating shot it looked all over.
But Rovers sent on Ryan Williams to give them width and suddenly the game was turned on its head.
Steve Elliott headed in from a corner in the 69th minute and two minutes later Walker scored his second converting a pass from Williams.