Lloyd Knibb had to "simplify" his drumming quite a bit in his later years but he was still very efficient.
As for the drum programmers, the best of them are more often than not artists who knew how to use a real drumkit as well,Sly, the guy from Firehouse Crew and Clevie are most probably on top of the list, much much less "stiff" rhythms than what the average programmer tends to do.
There are also a whole lot of amazing drummers in Japan nowadays, be they involved in old school sounds or heavy piledriving steppers (yes, the ones will REAL drums !). I don't know their names, though, but one plays in a band named Soul Dimension. Korey Horn, Eddie Ocampo,Ara Babajian and Scott Abels are also great drummers from the USA who have recorded many modern undeground classics with a heavy beat with their respective groups. The latter now drums behind Jimmy Cliff. They really can play any sort of JA sounds with a touch of their own, without ever losing the groove. Some drummers in the new wave of JA roots reggae bands are also very solid. I know the title of the post is about tunes but i'm too lazy to list them. If you feel like wandering off the beaten track, go check them, some sounds may not appeal to everyone, as they are not "purely" what is considered as roots reggae these days. One of Justin Hinds's sons is also a fine (albeit underecorded) drummer when it comesto rocksteady and original roots reggae.