Spellslinger is 3, so it was exact lethal.
(7:41) Trump is frozen, so the whole point of the hero power would have been to get outside Fireball range. The Mage has 26 health, so he makes the reasonable decision to build a board with Azure Drake and Harrison Jones. He's just very unlucky with how it turns out.
It wasn't exact lethal, he had 10 mana and didn't need to Fireblast thanks to a Flamewaker proc (though he hadn't even attacked with Flamewaker yet.
Refusing to trade his BGH for the Flamewaker seemed like a gross misplay to me. With Flamewaker alive, one Frostbolt or Arcane Missiles with a face proc leaves him sweating about both Fireball and smaller burn spells for the rest of the game
If you're leaving the Flamewaker alive, then obviously you don't hero power, because it doesn't actually bring you out of range of like, literally anything. If you're gonna go full ogre, go full ogre.