It appears your repo is missing information about version "3.74.gpl".
I downloaded a copy of the following files:
Extracted and scanned through the XML files respectively, and there is not reference at all to "3.74.gpl", which makes me wonder if this is why yum does not acknowledge its existence, when doing "yum update wbm-virtual-server" or "yum info wbm-virtual-server" (which reports only 3.73.gpl)
I know there are others who have seen this issue, and am surprised that it hasn't been caught on your end, and/or fixed as of yet.
Anyways, I hope this information helps, and results in a fix of your repo or explanation as to why the repo doesn't include 3.74.gpl as of yet, even though I know you released it weeks ago.