>I don't believe it's necessary to have multiple GPS antennas (one per device), unless signal path redundancy is required
Don't those splitters typically have an amplifier, so become a single point of failure?
If you're going through the trouble to have multiple time servers on your network, you probably want to make sure that an amplifier failure doesn't take them all down at the same time.
The antenna has an amplifier, usually with more than enough gain to support downstream splitting. But then sure the antenna is a SPOF.
Also the splitter will pass through the dc-bias on the first port to power the antenna, -- so whatever is hooked there is another spof.