@jkschneider commented:

I worry about this one. Mean isn't aggregable across dimensions, so doesn't seem particularly useful in general. For distribution summary type metrics, shipping a total amount and count is generally sufficient to be able to derive a truly aggregable mean. Some systems are so aware of this problem that they provide a standard query function OOTB (see dist-avg). Some monitoring systems expect mean to be pre-computed as a matter of convention, but could shipping mean be an exporter concern for those systems?