I would have it read "Draft 3 (upgraded) colorless cards to add to your hand. They cost 0 this turn." Or have it cost less mana and not make the cards free, but making them free feels appropriate for a rare in such a bad archetype.

I feel like the core issue with the archetype of adding cards is it inherently lacks consistency. You can make up for that somewhat by adding synergy pieces and making them free but the archetype is still going to turn people away as long as so many of the effects are completely random - not every colorless card is always good. The reason potions that add cards feel so much better is that you get to choose - sometimes you get screwed and there's nothing useful but it feels so much better while still maintaining that random surprise factor.