JTB Batch Change can simplify AutoCAD work like redefining blocks across many drawings.
On the Drawing List tab in the Excel file that comes with JTB Batch Change add all drawings you want to have updated.
This is the drawing I want to update.
On the Import tab select Block Definition as a command to use and select source drawing where the new block definition exists.
This is the updated block I want to apply to my drawings.
Select the row with the Import command and click on Run and select the drawings to update.
Here is the result.
There is much more JTB Batch Change can do. Take a look at the webpage and try it yourself.