The Primus seems like the guy that would rather give people a proper chance to redo and learn from their mistakes rather than simply harrow hell and fill his army with the damned.
He did, after all, expect Zovaal to meditate on his errors after an eternity in prison, and was sad he just became more evil.
Forsaken need a cultural shift while also retaining their narrative flavor.
Becoming a race of Formerly Damned Lordaeronians charged with a mission from the Primus makes perfect sense.