I think for Raytraced case it is due to how geometry data is being pushed to the render engine, along with the shaders.
Currently the shaders aren’t handled in the Raytraced layer very efficiently causing unnecessary trouble for the shader manager in the render engine.
I find though that I generally can make quite quick shader changes without slow updates, at least when I am playing with my shader graph tool where I can continuously update colors with speedy viewport reaction by the render engine without (many) crashes.
I did commit some fixes that should go out in the next WIP that hopefully makes things a bit more stable (but still far from ready).
All in all I think that changes to a material should trigger without much lag changes on the ChangeQueue. If you have a large amount of objects that need to be changed because of a material change that could potentially slow processing changes down. I hope that the aggregaton branch I’m working on will show a way to improve that.