mean w/o std dev is just pointless, I tend to reject them altogether.

If I am to record something like queue times (as in latency), I'd have multiple samplings of both time enqueued and entries (or approx entries size), provided the queues have a reasonable size() method (e.g. not O(n) and not blocking). Even having max entries increased with lower overall latency, it'd speak of bursty behaviour.

In that regard - Recording percentiles en masse (production) is rather expensive when there are thousands of metrics. The avg/mean + max require few bytes (sub cacheline) and it can be implemented lock-free.