I don’t think Varian has any Scourge PTSD I’m pretty sure he was rather uninvolved with any of it pre wrath.
But if we wanted to assume he does have such feeling then his actions after UC don’t make any sense as he leaves the forsaken almost completely alone afterwords focusing all of his major strikes on the orcs after saying he wanted to wipe out the “green skinned aberrations”.
UC might rightfully be what made him tip over the “kill them all” ledge but he was always focused on his hatred of the orcs and every thing else came second to him.
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The forsaken do nothing outside the line of horde rules until Wrath you can say being zombies is suspicious but as far as the horde goes they were on the up and up which is why the blood elfs join after the forsaken vouch for them.
The blight in WC3 and the forsaken blight are not the same thing.
https://wowpedia.fandom.com/wiki/Blight_(plague)
https://wowpedia.fandom.com/wiki/New_PlagueBlight is the term for the physical corruption of the land by the presence of the Lich King's undead plague. The plague affects all it touches, sterilizing the land, warping its natural inhabitants into bloodthirsty mutants, and twisting the local flora into disgusting mockeries of proper plants. The Eastern Plaguelands (most specifically Plaguewood) and the Dead Scar that runs through Quel'Thalas are perhaps the most startling examples of the long term effects of the blight.
The Royal Apothecary Society, the alchemical experts of the Forsaken, worked on various ways to use various parts from creatures living in their sphere of control as well as agriculture grown in the Tirisfal Glades, Silverpine Forest, and the Hillsbrad Foothills to create powerful toxins