Sorting in Hierarchical Address Book on Exchange 2013

I'm creating a HUB. For groups I set SeniorityIndex, but for users it is not set.

When the Outlook 2013 connects to the exchange server first time, all users are sorted in alphabetical order (Display Name). This is ok. (PhoneticDisplayName value isn't set)

But when Outlook 2013 loads OAB (cached), all users are sorted by creation date.

I want all users in the HAB sorting order to the DisplayName parameter value and lists the users in ascending alphabetical order. 
(But I do not want to set all users SeniorityIndex)

Please, help