if both raytrace IC and IDL IC are set using d3d's script, and IDL is used, then raytrace IC (the IC in poser render settings in current versions) is ignored.  however, increasing raytrace IC in poser render settings also increases IDL IC.  it might ameliorate those blotches by setting IDL samples higher, e.g. 1024 or 2048.  IDL samples variable is affected by IDL quality in poser render settings, but is set more easily via d3d's renderFF script.