Grimm seem to be evolving much faster than other species. Creatures are able to adapt themselves to specialized functions within their society.
As with the Hulking Grimm and Grimm Digger, the Grimmancer was sculpted by Christian Danckworth. I think he did a great job on all three and I hope that future Grimm are sculpted by him. Looking at the concept art for as-yet-unreleased Grimm in the Guide, there could be some fun minis forthcoming in the future.