HVDC is proven technology and used in many parts of the world. Line loss is not a reported problem. 
From Power Electronics Handbook:
"Modern HVDC systems incorporate complex control and protection features. The testing and optimization of these features require powerful tools that are capable of modeling all facets of the system and have the flexibility to do the evaluation in a rapid, effective, and cost efficient manner."
More info:
From ABB
  "HVDC and HVDC Light
HVDC (high-voltage direct current) is a highly efficient alternative for transmitting large amounts of electricity over long distances and for special purpose applications
As a key enabler in the future energy system based on renewables, HVDC is truly shaping the grid of the future.

I can't comment on your argument of heat energy loss. AVEC was working on a plan to convert that gas to energy using HVDC. I have forgotten what company they were working with