Hearthpwn

Ravenholdt Assassin costs 7, and there isn't a second answer, as there are no 5 mana 7/5 minions, and no other 5 Health Stealth minions except Stranglethorn Tiger, which would also need the Beast minion type to be specified, unless the rules have changed since I was last on here.

Shadow Bolt targets minions only, and Tail Swipe costs 4.

Next: 7 mana 7/7 At the end of your turn summon a 1/1 Boom Bot. (1 change, 3 answers)

The Pirate token from the Blackheart brawl has 3 health.

Next: 5 mana 5/5 Battlecry: If you're holding a Dragon, deal 3 damage.

Well, there's Leeroy Jenkins and Hemet Nesingwary, both with 2 changes, and Reckless Rocketeer with 3.

Next: 3 mana 3/2 Battlecry: If you control a minion with Taunt, gain +1 Health.

Perdition's Blade also has Combo: Deal 2 damage.

Next: 3 mana 3/3 Taunt. (1 change, 2 answers)

Ironforge Rifleman and Undercity Valiant.

Next: 8 Mana: Take control of a random enemy minion until end of turn. [1 change]

Ambush! and Moonfire are the 2 cards that come to mind.

Next: 4 mana 2/4 Battlecry: Choose One: Deal 2 damage, or Silence a minion. (1 change, 1 answer)

The answers are Bloodmage Thalnos, Kobold Geomancer, and Loot Hoarder. Mine is solvable, and is in fact an old puzzle that I solved a while back on this post, if you're all stumped and someone wants to looks for the answer. (It's pretty far back though.) Also, I don't think rarity counts as a change unless the rarity is specified.

Next: 5 mana 3/4 Battlecry: Restore 8 Health. [1 Change]

Mekgineer Thermaplugg is a Mech, and summons Leper Gnomes.

Again, mine (5 mana 3/4 Battlecry: Restore 8 Health. [1 Change]) was not solved correctly, so it is next.

When you play or discard Fist of Jaraxxus, it deals 4 damage.

Mine was still not solved, (5 mana 3/4 Battlecry: Restore 8 Health.) So I'll use it again.

Rhonin Has Deathrattle: Add 3 copies of Arcane Missiles to your hand.

Next 5 mana 3/4 Battlecry: restore 8 health. (1 change)

Is it Shadowfiend? (Different text and only 3 health.)

If so, Next: 1 mana 2/1 Battlecry: Deal 3 damage to itself. (1 change, 2 answers)

Rend Blackhand only triggers if you're holding a Dragon (too bad for him)

Next 4 mana 3/6 Freeze any minion damaged by this minion

Ancestor's Call puts minions from both player's hands in to the field.

Next: 1 mana 1/1 beast Deathrattle: Add a random beast to your hand from your deck.

I'm pretty sure Frostoise was thinking of Dark Peddler, (only Discovers 1 cost cards) and you're thinking of Gnomish Inventor (Has Battlecry: Draw a card instead of that text).

Next: 7 mana Deal 3 damage to all enemies, and restore 3 health to your hero. (1 change)