Jan, as you guessed, this is a different issue. It sounds very much like https://bugzilla.redhat.com/show_bug.cgi?id=1186485. So, as a way to verify this bug is fixed, can you try the following: Specify the log depot settings (nfs/ftp/smb) for each server in the zone you want to collect logs from instead of specifying the "zone" log depot settings. Then, try to collect logs at the zone level. I'll try to fix the other issue in that other bug. Please ping me if you need help or have questions.
Verified fixed in 5.3.3.1 - 5.3.3.1.20150210145146_14d1c48. EVM servers now collect their logs correctly, each on its own. A workaround (due to a separate issue being present) described above had to be followed in order to verify this.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2015-0261.html