Tamilnadu Express: தமிழுக்கு அனைத்து இடமுண்டு, அதேபோல் தமிழ்நாடு அதிவிரைவு ரெயிலிற்கு அதிக முன்னுரிமையுண்டு. அதிவிரைவு இரயில்களுக்கு எல்லாம் முன்னோடி தலைவர் - Sakthivel Srinivasan

The HWH Duronto was ER's pride providing an affordable yet quick travel to the national capital unlike the SDAH Duronto which served as a Rajdhani alternative. Unfortunately this train was destroyed by a politician, who is best of friends with the RM. Going from GC to mainline completely destroyed the credibility of this train! Who would pay extra money :-
1. For a longer distance travelled.
2. And Dynamic surcharge for a train that once had average speeds over 80 Kmph and now goes slower than the Poorva which does not have a...
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dynamic surcharge.
This is the answer to your question, as to why ER doesn't care much about it now. You must understand that this duronto was introduced to cater exclusively to HWH passengers first (DHN,DDU,CNB were tech halts at first) and not for some politician who thought of it as his father's right to intervene and destroy this train.
Regarding NCR's treatment of this train, NCR always treated this train bad because of it's lower MPS, but nowadays frankly even ER doesn't care how much NCR delays this train.