Southend then struck the woodwork twice in the space of 10 seconds as Ben Coker's free kick shattered the underside of the bar before Shaquile Coulthirst's follow-up header rebounded back off the foot of the post.
Coker was unperturbed though, and teed up Barry Corr with a precise cross 10 minutes before the interval, but the forward couldn't guide his header on target.
The Shrimpers were level at the break but went ahead less than 60 seconds into the second half as Matt Duke dropped Will Atkinson's shot at the feet of Coulthirst, who was left with the simple task of slotting the ball home from close range.
Michael Timlin then curled an effort narrowly wide of the post before Coulthirst came close to grabbing his second goal of the game when his deflected strike dropped just past the post.
In the 72nd minute, D'Ath arrived late in the box to guide a header into the far corner to level the score.
Southend's frustration at being unable to hold on to their lead boiled over in the sixth minute of injury time as Luke Prosser was shown a second yellow card shortly before the final whistle.