When Denethor leapt, flaming, from the top of that castle, did he kill any orcs or set any of their war machines ablaze when he landed? I really hope he did, it would have been a good redemption for him.
Unfortunately, it doesn't seem terribly likely - the rock outcrop he jumps from doesn't extend past the city's outer wall, and even at a full run, he wouldn't have travelled too far from the base of the outcrop.
More than likely, he would have landed amongst the soldiers fighting to defend the first gate - and would have likely further decreased their morale at a crucial moment (though, they probably would not have realised it was Denethor, having a flaming body splatter in your midst wouldn't be cheerful).
Well it didn't really happen, so no. Just PJ and his revising for effect on the audience....