It's also a 3/3 Creature, so it dies to everything but un-Revolted Push and Abrupt Decay. This card would have been better as an Enchantment, but even then it's still 4 mana on turn 5 to drain a target for 2, then repeat once a turn maybe. I doubt it would ever be playable against top tier decks.
Tested Bag of Holding (in Mardu 8-Pyromancers Midrange because it has 8 discard outlets and not that much graveyard abuse). One neat thing that came up is that Bag of Holding can semi-nullify Turn 1 targeted discard by soaking up the forcibly discarded card. It also profitably loots while you're Hellbent. Maybe combo decks actually want it in their sideboard?