Recommended Group setup

Current setup: We have three Administrators, managing 3 groups. Within each group, a couple hundred computers. Each group was created by the IT Director, and then shared with other Administrators. 

Is the above the best/recommended setup? More than likely not, thus what is a better setup?

Latest issue: Today, I created a test policy, and wanted to apply it to one computer for testing. But, after an hour of trying, and then even having to phone TeamViewer Support, I was not able to do so, since the group with the test computer was shared by the IT Director. Ugh...

Sounds like we need to restructure all our computer groups.

Thanks in advance for ideas/thoughts.