"Been thinking some more about this (never a good sign) and I reckon my work will improve greatly
if I use Poser less for the final image and more as a base to work from. 
Combining Poser - and using it in different ways - with other graphic elements will probably
get me closer to my - ahem, pretention alert - artistic vision"

I think you nailed it,.

Don't let the tools set the rules!

For me Poser is a means to an end, I churn out tons of Poser animations which are the raw material of my VJ shows.
(love music, can't play a thing, but found a way put visual art to music)
Like others who've posted here, I've watched as new developments in the software have set new standards in realism, etc. and tried to learn as much as I can and incorporate it
where appropriate but not get overwhwhelmed by it or let it slow me downn too much
(insert dark muttering about render times)
   Every now and then
I find myself asking the same questions as Sam's original post and my way out is very similar,
look for a new approach,try  new technique, do some experiments
recognising the problem is the key thing, well that and lighting.