Looking at stats, both before and after Chopper3 retired, Mark, Splattne and I have been handling more flags. Mark & splattne more than me, since their overlap with Chopper3's historic schedule is larger than mine. The numbers are inflated right now due to certain users going through old off-topic content and flagging extensively, and such users tend to do so on my watch for some reason.
That's a good point though. All it takes is one high flag-rank user to expend their entire flag quota in 30 minutes to turn the mod-queue into it's usual no-higher-than-9 into an intimidating 46. I do look at each case individually to see if I agree with it and to figure out exactly how to handle it, so I'm putting in as much work as the flagging user in this case.
At the moment, me, Mark, and Splattne are all in the triple digits for handled-flags in the last 30 days. Zypher and Sam are currently tied. Before retirement, Chopper3 was the top flag-handler.
Do we need a third moderator? In my opinion only, if we can get another me or a Mark around UTC+0 or so we'll just fine with two. Our most active flag-handlers seem to be least active from UTC 0900 - 1600. In my case it's because I'm sleeping and then dealing with dayjob morning issues.
One caution about more moderators is inconsistency. The more of us there are with the hammer, the more individual interpretations there are about where the edge cases belong. We can 'do better with better communication,' but with all of us on the three corners of the globe that kind of discussion is hard to have.
There is more, but I've run out of breakfast. More in several hours when I have time, since today is a datacenter day for me.