Fermanagh star Eamon Maguire, Paul Cosgrove, Pat Cadden and Jason Cadden were also on target for St Pat's in the first half while Cassidy (0-2) and Ryan Jones notched Derrygonnelly's points.
Substitute Paul McCaffrey gave St Pat's some vital breathing space with a score to make it 0-10 to 0-8 but Ward's point at the start of injury-time left the minimum between the sides again.