When you use Hidden Blade to kill your own unit, do you still draw 2 if you use Sett to sworn a buff to revive?

Yes, you still draw two cards.

According to RiftJudge FAQ #8540 and #2372, when you use Hidden Blade on your own buffed unit and use Sett's (The Boss) legend ability to save it, the draw effect still occurs.

Here is the breakdown of why this works:

1. Replacement Effect: Sett’s ability acts as a replacement effect that intercedes during the resolution of the "kill" instruction.
2. Tracking the Controller: Because the replacement effect only modifies what happens to the unit (recalling it to base instead of sending it to the trash), the unit remains a valid referent for Hidden Blade.
3. Successful Resolution: Since the unit was a legal target when Hidden Blade began resolving and the controller can still be identified, the draw instruction of the spell successfully executes.

Important Note: The unit must be at a battlefield when Hidden Blade begins resolving for the spell to target it legally. As long as you use Sett's ability during the resolution process to replace the "kill" with a "recall," the controller is still identifiable, and you get your draw.