AutoCad :: Blocks Coming Into Drawings At Wrong Scale

I recently started working at an Electrical Engineering firm and one of my many tasks is to sort out their AutoCad system and bring it up to date! An issue that has only recently started happening is that our blocks don't insert at the correct scale. Some of our drawings are metric and some are imperial, and currently all our blocks are in one Imperial file (reference file for our palettes). Is this our issue, my understanding is that when you create a block you should create it as a wblock and each block should have its own file.

The problem is that some of our blocks we want to come in at scale ex/ a 2'x4' light fixture, however an electrical socket or light switch symbol we want to come in at a slightly enlarged scale so that you can easily read the drawing and see where they are located.