Mothiba started on the bench after battling with an injury that saw him withdrawn from the Bafana Bafana squad that faced Libya last weekend.
Dolly, meanwhile, made his first start in Ligue 1 this season, but his evening was cut short after picking up an injury.
Despite the early set-back, Montpellier broke the deadlock on 50 minutes thanks to a strike from Damien Le Tallec.
Mothiba was then brought on four minutes later, replacing Ludovic Ajorque.
The South African striker had the final say as he netted the equaliser in the third minute of time added on to seal a point for Strasbourg.