"We are drowning, we need to hire"
Start with message volume over a long enough range to show a trend rather than a bad week. If incoming volume is flat and the feeling of drowning is new, you do not have a demand problem, you have a distribution or a process problem, and hiring will not fix it. Look at the same period account by account. A team where one account carries most of the inbound while others sit idle looks exactly like an understaffed team from the inside, and the fix is routing, not headcount. If incoming volume genuinely is climbing while response coverage falls, that is the case for hiring, and now you can show it.
"Our response time looks fine, so why are people complaining?"
This is almost always the coverage gap. Average first reply only counts responses that arrived within an hour, so a team that answers the easy half of its messages quickly and never gets to the rest will post an excellent average. Read coverage next to it. A high average with weak coverage means the conversations that go unanswered are invisible in the number you have been reporting, and those are the people complaining.
"Replies are slow on Mondays and nobody knows why"
Open the activity heatmap before changing anything. It shows which days and hours actually attract incoming messages, and the answer is often that the peak has drifted away from the shift pattern that was designed around it months ago. Weekend demand that nobody covers arrives as a Monday morning backlog, which reads as a Monday staffing problem and is really a Sunday one. Once you can see where the demand lands, coverage becomes a scheduling decision rather than a guess.
In each case the method is the same. Hold the period steady, change what you group by, and read coverage and speed together rather than separately. Numbers that disagree with each other are usually telling you the problem is not where you assumed.