Sure, losing to ragnaros taking out your best creature instead of any of the small 1/1 bait sucks. But IMO, card draw RNG is the worst.
Shaman (me) vs Priest. I went first.
Round 1
I play an unstable ghoul.
Opponent passes.
Round 2
I play a nerubian egg, attacks face with the ghoul.
Opponent heals self.
Round 3
I play ANOTHER nerubian egg, and attacks face again with the ghoul. At this point I am smiling VERY broadly... because I have a rivendare on my hand. All I need to do is to get my ghoul killed next turn!
Opponent throws out a Wild Pyromancer. JACKPOT!
Round 4
I play Baron Rivendare, attacks his Wild Pyromancer with my Unstable Ghoul. Ghoul dies. Boom. Two times one damage to every minion, which kills my two eggs, which spawns two times two 4/4 hatchlings. I'm now sitting on 16 attack worth of creatures, and there is pretty much no way I will lose. Best Card draw RNG ever, really. Any opponent at this point has to be cursing loudly!
Then he plays Auchenai soulpriest and Circle of Healing.
I proceed to lose the match quite badly.
That's the kind of card draw RNG I seriously hate. Yeah, I should probably have seen it coming. But still. I drew the perfect hand, and I lost to the perfect counter. Sad day. Card draw RNG sucks