It took a late penalty from Jamie Hamill to secure a point for the Jambos, but their coach insists that they showed resilience against the high-flying Dons.
"They are improving and getting stronger and I think you can see that again," Sky Sports News quotes Locke as saying. "They acquitted themselves brilliantly, especially in the second half, against a top team, even when we went down to 10 men.
"It would have been easy to put the heads down but as usual we got the response we were looking for."
The result leaves Hearts bottom of the table, 18 points behind 11th-placed St Mirren with six matches remaining.