If you use Hidden Blade on your own unit and save it with Sett's legend ability, do you still draw 2 cards?

Ruling: Yes, you still draw 2 cards. Hidden Blade's kill effect and draw effect are separate from each other, so the draw happens regardless of whether the unit actually dies.

Nuances:

• If the targeted unit leaves the battlefield before Hidden Blade resolves (bounced, banished, recycled, or killed by another card), the target becomes illegal and nobody draws cards because the controller can no longer be determined
• The unit must still be at a battlefield when Hidden Blade resolves for the draw to happen
• If the unit moves to a board-zone (base), its controller can still be determined and draws two
• If the unit moves to a non-board-zone (hand, deck, trash, banish), there is no controller to determine and nobody draws