Just one person for the nightshift seems to be not very safe for air traffic, and it isn't healthy for the ATCO too!!
At what point do things get safer or more healthy? And what are the hazards and risks that concern you?
I've worked 'one-man' night operations, not at a hub it must be said, but it seemed like a perfectly sound operation to me. Plenty of perfectly adequate mitigation for hazards both for me and for the aeroplanes. At another small airport with not much more traffic we worked two people on a night shift and it was routine for one person to take a long 'break' for most of the shift so, for practical purposes, it was the same as one-man' ops in many respects.
What matters is that a proper assessment of workload, human factors stuff and safety is done to establish the minimum number of staff needed for any particular time of day or operational circumstance.