Thanks for working with me Jonathan.
I ran a 1=1 query on the map service (layer 0) and it returned all 37 in less than a second, same result several times.
The same query via feature service layer zero took 2 to 4 seconds each time.
I've noticed in Chrome Dev tools that a bunch of queries are fired off to AGS from the client... like 15... all are in a wait state, then about 30 or more seconds later, they trickle in and finish.