I did LGW-DEL in a 757 two months ago. We had a redued pax load so were able to go direct, if we had been carrying the full 90 pax (VIP config) we wouldn't have made it.
Its not just the weather and pax load that affects these kind of routes, you have to have a good look at the alternates available. Not many of India's airfields have ILS and certainly not Cat111. You can find yourselves diverting to somewhere that would be unfavourable on a low amount of gas!!
