The Latics have scored only once since the duo left in the January transfer window, as an injury to winger Antonio Valencia compounded Bruce's woes.
The former Birmingham City manager fielded Amir Zaki as the lone front man in Saturday's goalless draw with Middlesbrough, with Oliver Kapo playing slightly deeper.
But Bruce soon realised this wasn't the solution to his striking problem.
Struggle"I don't think playing Kapo in the role we did really worked, and up front we have started to struggle a bit," he told the Wigan Evening Post.
"With Heskey and Palacios going, and Valencia injured, we've lost a little bit of the cutting edge we had.
"We have always been a difficult team to beat, but at the moment we're missing creativity in the final third of the pitch.
"But we'll keep working on that aspect of our play and hopefully we can get things right going forward."
On Saturday, Kapo and Zaki were replaced by Antoine Sibierski and new signing Hugo Rodallega respectively. Bruce claimed his side looked more likely to score after the substitutions had been made.
"At Boro we looked a bit more threatening when Rodallega came on, while Sibierski gave us composure," he added.
"I thought we had two or three good chances towards the end, but unfortunately we didn't take them.
"In the end I thought it was a decent result, especially when you consider all the changes we've had to make recently.
"As the second half went on, there was only one side who was going to win it and that was us."