Blender has had some tolerably decent decimation scripts, at least in the past.  I'm not sure about the current version of Blender.

The main problem with most decimation techniques seems to be the quality of the resulting reduced mesh.  The poly count may be reduced and the basic shape may be retained (minus some detail), but for Poser figures (specifically for the joints) you'd really want a method which would create a mesh which wasn't messy, with irregular polygons.  Preserving the edges of actors could be a problem, if an entire figure .obj is reduced.  The methods I've seen invariably create all tri meshes which are very messy and require a lot of manual cleanup.  In some cases, UV mapping is lost or damaged by the decimation.  I've never seen a decimation tool which would retain groups, as far as I can recall.

Remeshing processes, with more user control or input into the process, would probably be more promising for figures than the usual automatic mesh decimator.  I keep waiting for quad-meshing techniques to start appearing in the 3D programs which are affordable on a hobbyist's budget, but I haven't seen any yet.  :sad:

A figure can be successfully reduced and remain usable, apparently, but the process isn't easy, as I understand it.  JoePublic once created a reduced version of Miki.

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.