Hi Marko,
Since you are creating the DGs in AD, and not via an Exchange mechanism, AD does not include necessary Exchange attributes. These attributes must be populated with data so that DirSYnc knows to sync them up as DGs and to also enact changes on them.
Please ensure the following 4 attributes are filled out, via ADSI edit or your choice of attribute editor:
Now, since you created them in AD, unless you populated the 4 following fields in ADSI edit or your flavor of attribute editor, they will sync up as security groups. They are:
1. DisplayName
2. Mail Nickname (Alias)
3. ManagedBy (Set in ADUC, not in ADSI, DGs in ExO MUST have a manager set)
4. ProxyAddresses or Mail (smtp value)
Note that if the DGs are missing this data, changes to the DGs may not be grabbed via DirSync.
Hope this helps,
-Victor