Delhi - Chennai is Fully Electrified Double Line route while Delhi - Bangalore is not. Secunderabad - Bangalore is a 600 km long Single Line Diesel route (Which 22693/94 Rajdhani takes from SBC-KCG) and another is a 700 km long diesel route which is 50% doubled and 50% single (Which 22691/92 Rajdhani and 1213/14 Duronto takes). Loco Change at Secunderabad/Kacheguda takes almost 30 mins. Moreover, the Secundarabad - Bangalore route is pathetically over congested.
It is not possible to either reduce the journey time of existing trains or introduce a new a train that takes less than 30 hrs b/w Delhi and Bangalore unless Secunderabad - Bangalore line is doubled and electrified (which is not going to happen till...
more... 2020). Electrification b/w Bangalore and Secunderabad is expected to complete by 2015 but there is no proposal to double GY-SBC line Yet. SC - GY is almost doubled except for a single stretch from Matmari - Mantralayam Road, which has just started.