DBRG Rajdhani is a curious case. You can see good occupancy throughout the year, but you cant be sure whether all of those are a result of stations before KOJ! Stations between KIR-DNR get good bookings in these trains & reservations are made starting MXN or NTSK with boarding at these stations.
This is just like the erstwhile BP Mail which on peak seasons used to run full till DGU, but only on paper, while in reality the train used to shed a lot of passengers by Malda. This happens probably because the 3AC & even 2AC tickets are quite comparable with flights from Bagdogra & sometimes even Patna.
This...
more... however does not mean that NFR does not fill this train. DBRG Raj not only serves Assam but also Nagaland, & Sikkim & other adjoining regions.
The old arrangement of slip coaches between GHY-DBRT was probably useful with these facts and also that GHY to NJP also gave good amount of passengers. Post LHBfication & in recent years stations, stations beyond KIR have been occupying a good share in bookings.
Speeding up of these trains will make them more competitive. However, the very fact that the National Rail Plan has set up a target of 2051 for HSR at Guwahati shows Railway's interest to upgrade speeds in these regions.