Single AD for Large Organization with Dev/QA/Prod OUs to split things up?

My organization is tossing around merging AD into a single domain. My gut instinct is against this as I've never seen it. I started compiling pros/cons and there are both.

The design would be 3 top level OUs for Dev, QA, and Prod then split by users and computers and the usual steps.

GPOs would be limited to the appropriate OU.

Pros:

* Fewer servers
* Easier integrations with Azure/AWS/etc
* Easier management of AD (roles, global catalogs, etc)

Cons: …

ad cybersecurity dev large prod qa single things