I've also seen highly user-visible performance issues because some developer either didn't realize how slow performing a series of queries in a loop would be (didn't understand the network overhead of each request) or didn't know how to condense what they needed to one or two requests. High correlation of this with the ORM-dependent folks.
So far as averaging a few days of stats my gut feeling is "this can just be a view with one or more medium-complexity selects behind it" but maybe there's some reason it can't.
> So instead, I kind of created my own ORM / interface where I can quickly write queries on my own and use those in the code. This is especially easy since most the queries can be written in postgres functions so the strings of those queries is incredibly tiny!
I haven't been in non-Rails Ruby land in quite a while but I remember liking Sequel quite a bit. Very much The Right Amount of abstraction (i.e. barely any) over the DB.