It depends on a lot of factors, but even second granularity gives you a 60x reduction in the thundering herd. Whether more is needed or even possible often depends on the specific problem domain. For example, if your task takes 20ms, us granularity doesn’t help. Indeed it makes it worse if you’re using randomization because there’s a lot more microseconds than seconds so you can end up with a lot of work that ends up in practice still getting scheduled together due to other delays.

You want your jitter to be significantly >> than the time your task takes as otherwise you get non intuitive degradation that can reintroduce the problem you’re trying to solve. It’s a balancing act picking the jitter that drops off the thundering herd enough and one that is still greater than the time your work takes.