I don't think you can guarantee the generation of anything sequential across multiple machines without some sort of authority. A single machine, sure as long as the resolution you're using is small enough and/or you have a single point of authority on that machine.
But across multiple machines?
Can you explain to me how you're doing that across multiple machines without any sort of authority? If there's a way to do that I'm genuinely curious.
Most simply use the system clock. Now if I would was building a machine critical distributed system I would advise against using the system clock and instead use some sort of logical clock. But in this case the clock doesn't need to be super accurate, it just needs accurate enough it get placed near the end of the table.
But the worst case in this instance is your insert is slow, and fragments your index. I trust infrastructure to make sure the clocks are accurate.
But across multiple machines?
Can you explain to me how you're doing that across multiple machines without any sort of authority? If there's a way to do that I'm genuinely curious.