Maybe it's not the spectro, just the software/monitor combo you are using ?
I recommend you drive the i1 with Basiccolor or ColorEyes software.
I use Nec 2190UXi with Spectraview II profiler. It calibrates TRC using 12bit internal monitor LUT, with 256 steps, average low light measurements, and best grayscale color tracking. It gives good results in light parts, or when the panel's set to high luminosity levels, but the darker the sample is, the worse effect it gives, so I suspect it is a matter of device.
BasICColor doesn't work with non-Spectraview Nec, and the trick that turns SV mode doesn't work in my panel, but I'll take a look at ColorEyes.