After several weeks of trying to get the issue resolved I have just received this from Dymo:
I am sorry to inform you that your CardScan model is not going to be compatible with Macintosh OS X® 10.11 El Capitan.
PLEASE NOTE: CardScan scanners are only compatible with OS X® 10.8 through 10.10. On other versions of OS X®, CardScan scanners and software may be used in a virtual environment with compatible versions of Windows®.
This only applies to CardScan Executive. CardScan Team and CardScan Personal are not and have never been Mac compatible.
If you have recently purchased the unit, please consult the return policy from the place where you purchased the product. If you are outside of their printed policy, please provide proof of purchase and return the unit to the following address for a refund of the purchase price (excluding shipping & applicable taxes):
DYMO CardScan Return Service Center
c\o Newell Rubbermaid
1660 Railroad Ave
Shelbyville, TN 37160
Not what I wanted to hear, especially as others have reported 10.11.4 has resolved the issue. Returning the scanner for refund is not an option for me, so I guess its bound for the bin - great!