There are reasons why it doesn't help quite as much as you'd think:
1. While there is a slight increase in probability, it is an inefficient solution overall. Once you get beyond a certain point, you mostly end up with a surplus of moderators who aren't doing anything. And since they're out of practice, their performance might suffer.
2. It's mostly an issue with the people who would be good at it having generally the same schedules. If you CAN get it, it might be a good idea to go for people who are on at odd times & would make good moderators, but it's generally not an available option.
As for Reporting, I've rarely been on the end that looks into the reporting, so I can only guess at how that would work. The problems that I might expect would be diffusion of responsibility, where no one reports because they all expect someone else to, & report trolls. Report trolls meaning if you have a forum with an anonymous report function, they'd spam that to give the mods useless shitwork to do & hopefully harrass a user or 2 in the process. In a chain of ironic drama, reporting might get used as a platform to legitimize your flaming, prompting a rule not to announce reports, making diffusion of responsibility more likely.
Like I said, you have to figure what is just enough.
This is generally the Golden Rule.