Welcome to LQ.
The first question is "why do these 2 users need write access to DocumentRoot?"
Uploading content?
Generally, I'd add them to www-data group using
Code:
usermod -a -G www-data <user1>
usermod -a -G www-data <user2>
and have them logout and back in.
Did you 775 recursively?
Writing
in DocumentRoot and writing beneath it is another matter that will require
/path/to/DocumentRoot