DH was an intentional compromise that Colemak took to increase QWERTY compatibility and Colemak documentation has always acknowledged that, so I respect it isn't perfect, given trade-offs, but as Workman acknowledges changing DH has a knock-on of changing a lot of things that I like about Colemak.
I think Colemak also better optimized some trigraphs over Workman's digraph focus.
That said, the difference between Workman/Norman/Colemak/Dvoarak is all rather "slight" compared to the respective distance between Qwerty and any of them, so some of these distinctions truly are "micro-optimizations". Most people would do better to learn any of them than keep with QWERTY whether or not they can tell which one micro-optimized better.
I think Colemak also better optimized some trigraphs over Workman's digraph focus.
That said, the difference between Workman/Norman/Colemak/Dvoarak is all rather "slight" compared to the respective distance between Qwerty and any of them, so some of these distinctions truly are "micro-optimizations". Most people would do better to learn any of them than keep with QWERTY whether or not they can tell which one micro-optimized better.