One question with the use of the term 'dark halos' is whether we are talking about a dark baryonic halo or non-baryonic halo. In your link the paper was referring to an HI region, and obviously we would not be able to detect a non-baryonic DM halo without some stars as a tracer for its gravitational potential well, but which exactly is being predicted by the CDM model in this respect?
I believe the CDM model requires the existence of lots of non-baryonic DM in dark halos to encourage the condensation of sub-Jeans mass baryonic clouds into galaxies etc. That process could still be going on today.
The observation linked to is that of an HI region of galactic mass in the IGM of the Virgo cluster. Obviously there is a lot of baryonic matter out there as well as any non-baryonic. What, I wonder, would be the contribution of these dark baryonic HI regions to the total cosmological density parameter?