(Both on stable and dev branch)
Starting Defend Kamino or Defend Syrta on a DEDICATED server without a player assigned as Zeus will result in no units spawning at all, so nothing happens.
However on a non-dedicated server playing without a player assigned as Zeus works 100% fine, the AI will spawn waves and the mission works out as planned.
I'm not 100% sure, but I think there is the same issue with the Seize missions.