I would like to ask for the sake of both possible rolling of a Sith Pureblood Warrior and the Legacy unlocks and tree, whether there is a TOR Canon consensus that Purebloods and Humans could intermingle and have children? It is my impression from the game that Purebloods (i.e. descendants of the exiled Human Dark Jedi and the original Sith species' higher castes) and Humans can indeed mate (see Lord Abaron's quest). The original mixture had taken place thanks to the Sith Alchemy and the mastery of the Dark Side by the exiled Jedi, but since then the mixed offspring ("Purebloods") were genetically compatible with Humans and can be considered near-Human.
Can any of the Pureblood SW confirm that during one of the conversations with Dark Side Jaesa
In the general Star Wars lore, there seems to be a consensus that this interbreeding is possible, see http://starwars.wikia.com/wiki/Sith_%28species%29
, section Hybridization.
Essentially, it seems like that to be considered Sith Pureblood, one had to display enough visible Sith-like traits (see above noted quest for Lord Abaron), otherwise one could be considered Human but could still have strong Sith blood (albeit without the visible traits). In both cases, the Sith Warrior, would be an heir of both the Dark Jedi and the original Sith, but in the Pureblood SW his Sith legacy would be visually distinctive (albeit e.g. Exal Kressh had like only colour of her skin and her yellow eyes to show for her Pureblood status), while in the Human SW his Sith legacy (that he takes pride in, as can be seen in his interaction with Inquisitor Arzanon) would be not visible visually (but it would of course made itself manifest in his affinity to the Dark Side of the Force).