Dehradun needs a connectivity to IT cities like Hyderabad, Bangalore. There should be a train connecting dehradun, haridwar to hyderabad , bangalore. Maybe a train from Dehradun to Mysore via SRE-MTC-NDLS-BPL-NGP-SC-SBC.
Delhi to dehradun there is already premium train like Shatabdi. And as mentioned above that Jaipur to Dehradun tejas might be a good option.