** Overhaul 6/27/21 **
Mulligan for a way to deal with the 10/10 on Turn 4, one is usually enough.
Sap, Assassinate, Big Game Hunter and Doomsayer(played on Turn 3) can kill the 10/10. The exceptions: Scarvash makes BGH and Assassinate unplayable on Turn 4, Archaedas and Lady Naz'Jar will turn your Doomsayer into something else. If you can't deal with the 10/10 on Turn 4, a RESTART in PROBABLY in order.
Turn 1 - Pass.
Turn 2 - Hero Power
Turn 3 - Play Doomsayer, Tar Creeper if no DS, or pass.
Turn 4 - Kill 10/10 if you didn't play Doomsayer.
Key points of the deck: You should probably play Lab Recruiters on Coldlight Oracles. And, ideally you want play Brann, Coldlight and Lab Recruiter on the same turn. You need the extra cards in your deck to avoid fatigue. Rafaam has Entombs, so most of the time his deck is effectively 32 cards, unless you mill his Entombs. If you only shuffle 6 Coldlights into your deck, you are only ahead on fatigue by 4 cards. This may not be enough because Rafaam is immune 2 of every 3 turns, that's why the 3-card combo above is important. You can also Lab Recruiter a Lab Recruiter, so you can go infinite then, if necessary. The Shadowsteps are MAINLY for the Coldlights, but sometimes they work well on the Lab Recruiters to shuffle more. Again, shuffling only 6 cards into your deck may not always be enough.
The key to survival is to deal with the 10/10s on his turn 3, 6, 9, 12, 15, etc.
The Player Artifacts mostly have good utility. The bad one is Medivh's Locket, which just clogs your hand. Try to get the Shard of Sulfuras(5 to all) or Loathar's Left Greave(3 to all enemies) for Rafaam's Mirror of Doom(board full of 3/3 Mummies). Betrayal + Hakaari Blood Goblet(transform a minion into a 2/1 poisonous snake) can also set up nice board clears.
Like all my decks, if you want to duo play with me, PM me and we can be friends on NA.