800+ km is going a little too much for a daytime train, especially for routes where mps isn't high either [Judging by the average of the other trains, the mps can't be too high; does it touch 130 kph for much of the distance either?]. Even if it does an average of 80 kph on this route, it'll still be a back breaking 10 hour journey that can better be salvaged with an overnight train, IMO.
Also,I just checked that both the cities are also connected by air. So, a business traveler...
more... who really puts a premium on their time will never choose a 10 hr VB over a 4 hr flight [including check in time; the actual flight time is 2 hrs]. Maybe if the intervening stations are big enough to give significant pax, then it might be good enough to run, but purely for end to end purposes, an overnighter with a fast TT is better.