Currently, the Congressional staff is mostly recruited and retained by the congresspeople, and they become the experts in many situations. They can also be retained by the committees, in which case they are often more non-partisan. They do have some ability to influence the debate, but they usually do not frame it.

If we had national assemblies by sortition every 2 years, I would worry that the the tail (the current structure of Congressional support staff) would wag the dog. A better system would need to be designed to enable good decision-making.