Not at all, Darth is from Dark Lord of the Sith, so it's a Sith title. A dark jedi master is something completely different than a sith, it's more like an evil jedi eg. Assajj is a dark jedi, Dooku is a Sith Lord=darth Tyranus.
Darth isnt a Sith title and was misused in KotOR 1,
Darth is a dark jedi title,
Sith get their own titles unless they are not following the basic teachings of a sith, thus being a sith and having the title darth
And your confused between the Sith Empire and the Galactic Empire
And since Tyranus was the emporers lacky he was not a Sith
The emporer and "DARTH" Vader were not Sith, as they did not follow any of the rules and merely wanted to control the galaxy by wiping out all force sensitives, not just jedi, whereas a sith regime would of spared jedi which fell to the dark side
You don't know Jack about the Sith.
Darth is a Sith Title, not misused in KOTOR. For it was Lucas arts/film who said that Darth's were around during this time.
The Sith were once a species, that died off, but like KOTOR said the sith of today are followers of an ideal. Sith, because they follow everything that makes a sith a Sith.
Exar Kun wasn't trained by Marka Ragnos, he was trained by Freedom Nadd. Marak just made Exar and Ulic Sith so that they could keep the power of the Sith going.
When Bane became the only Sith Lord left, he made the rule of two, and used the Darth Title for his new way of the Sith. Even before Bane there was a Darth Rivan.
Palpatine and Maul continued Bane's tradition, and are both Sith Lords, as is Vader. They don't share blood with the old Sith, they are just followers of an Ideal.