Dynamic Distribution List question

The environment is Exchange 2013 servers in an organization of 500-600 users.  We have a "nationwide" DDL.  It triggers on the company initials being in everyone's AD attributes.  It's not working.  I have a series of questions I guess.

First, I initially advised against using a DDL for such a large group.  Too many people, too much dynamic info changing and I felt it would fail a lot.  It does fail a lot.  Against my advice, the admin went with a DDL for our "nationwide" emails triggering off of a field in which is supposed to reside the company's initials.  Like I said, it's not working and I was asked to fix it.

At first I thought, hey, I'll just make a new "nationwide" DL (without the dynamic) and be done.  Then I thought I wanted to actually FIX the DDL.  

So, IS a DDL for a group that large a bad idea for the reason I dictated or should a DDL for 500-600 users work just fine?

Second, where do I start troubleshooting WHY is doesn't work for everyone?  Do I look at the field it triggers on and then look for AD users without that field?

Any thoughts, advice, input, etc would be appreciated.

Thanks

Cliff