Ryans Zombies is a massive performance hit, according to every server host that has ever used it. They say it is badly optimised. Maps can also affect performance sometimes, hosts say the Chern. Redux is a performance hog, for example.
Personally I would not be bothered by those numbers, and only really be worried when players come to you with reports of server lag -
(which is VERY different from client lag, and often includes things like AI rubber banding over 30 meters, or building objects not saving because the Database is struggling)
- or stuttering or worse, like not being able to connect to the server at all.
for more info, you could repeat the test with only Epoch active on Altis, this way you get baseline and you modded server results.