The /etc/cron.d/sysstat file that's installed with USE=cron in place is no longer being installed with 11.0.4. I've confirmed that it is being installed with 11.0.2, which explains why sysstat isn't reporting anymore on my machines.
Please post your `emerge --info app-admin/sysstat' output in a comment.
Still no sign of your build.log or `emerge --info' output. Please try with -r1.
It appears that this bug has been fixed/obsoleted by making the installation of cron file manditory/automatic in sysstat 11.0.5; the cron USE flag has been removed. However, that causes a different problem to surface; see #531032. The /etc/cron.d/ file that gets deployed is in a format not supported by dcron, thus causing errors if dcron is in use. In that bug I've attached a patch that re-introducing the cron USE flag, since I did not want the cron jobs anyway.