In working through my TB18DC issues, it was finally escalated at Dell. I had provided Dell with a list of all the drivers I had updated (after re-installing the Win10 OS), and one driver update was missing. It is...

Dell Docking Station Firmware Update ....

Here's the catch. If you go into Dell's site using your workstation's service tag (or, anything else identifying your specific workstation/model), you're not going to see this driver update. The update is specifically for the TB18DC.

To get the update...

surf to https://www.dell.com/support/home/us/en/04
enter "TB18DC" and search
select "Downloads & Drivers" to narrow the results (should be '6')
select "Dell Thunderbolt dock TB18DC Firmware Update Utility

Once downloaded, run the utility with the TB18DC connected. There are directions provided for what to do once the update is successfully run.

It did not 100% solve all of my issues, but it is "much better". And, it avoids hours of hassling with 1st level Dell support, not to mention re-installing the OS and having to update both the OS and all of Dell's drivers/utilities, and re-establishing your dev environment because it got wiped out during the OS re-install.