Five mana for only five loyalty is a lot, and Ob isn't particularly good at anything
Discard and disruption By attacking the opponents hand early, black can slow combo decks and remove key answers before they matter
Vault 12: The Necropolis Wasteland Raider Acquired Mutation Assaultron Dominator Bottle-Cap Blast Crimson Caravaneer Duchess, Wayward Tavernkeep Grim Reaper's Sprint Ian the Reckless Junk Jet Megaton's Fate The Motherlode, Excavator Mysterious Stranger Plasma Caster Powder Ganger Rose, Cutthroat Raider Synth Eradicator Thrill-Kill Disciple Vault 21: House Gambit Veronica, Dissident Scribe Wild Wasteland
The value of X is determined only once, as Azlask's last ability resolves
The thing is that you can combine madness with cycling, draw some cards, buyback it and kick it with enough mana, all at the same time
Run an exile deck to capitalize on its static effect of dealing 2 damage to opponents and gaining 2 life for each spell cast from exile