Have you noticed latency when selecting objects in Civil 3D 2015 and 2016? Civil 3D seems to analyze the layer list when executing the move, copy and other commands thus causing latency. I have found a solution for the issue. Create a layer filter with no XREF layers then set it current then AutoCAD will only analyze the layers in the current file. I have created a LISP file to create the No XREF Layer filter. Place the LISP file in the Tool Palette to easily run in CAD files. I would also create the filter in the drawing template (.DWT) file so every new file will have the filter.
Copy the text below for the lisp file.
;Import No XREF Layer Filter
(defun C:lfilters ()
(command "-LAYER" "filter" "N" "P" "All" "NAME==\"~*|*\"" "No XREF Layers" "x" "")