I don't think the swtor writers retconned anything. They just didn't do their homework and lazily wrote in Hord's accomplishments, regardless of the canon timelime.
__________________ There's a man goin' 'round takin' names.
An' he decides who to free and who to blame.
Everybody won't be treated all the same.
There'll be a golden ladder reaching down.
When the man comes around.
The problem is that Freedon Nadd can be hardly classified as Sith Lord. He displayed no traits of them(except for the lust of planet conquering) Even, then, he stopped at one.
I would daresay, the new lore regarding Nadd has been mistaken about his nature as Dark Side warrior. It's obvious that Nadd should be classified more as a Dark Jedi rather than a Sith Lord.
__________________ RealistRacism: "Sheevites, much like the Banites, were meant to increase in power with each member. From Lightsnake to Gideon to Azronger, this was supposed to be the case. However, knowledge must've been lost in some kind of Gravid-like incident, as Az turned out to be a mid-tier debater with a sub-par track record, sh!itting all over Tempest's legacy. Sad."