Kelly,
we are working on popups and data tables so the feature layers are useful.
The need to access layers individually is to allow the user to choose layer visibility, maybe certain layers from a service are not useful for a specific map\application.
Take for example this service from the Northwest Territories.
GNWT/BiologicEcologic_LCC (MapServer)
Very good source of information but I only need a few layers for a mines project study.
To get back to the symbology problem, it seem that this is normal and not a problem from the setting of the service itself.
I did not think that red 45 degree lines to be complex but I don't have a clue as to how the render-er operates.
Is there other symbology service publisher should stay away from if they plan on using feature layers?