The first time I got killed by that deck, I used to think like you. I thought it was sooo overpowered…
Then I played the deck myself and realized you only had 25% chance every turn to have the right hero power ( 2 mana discount ).
Furthermore, you also need to live long enough to get your Reno Hero and play it.
Furthermore, you need to have the Coldarra Drake in hand which is very vulnerable to Dirty Rats, Theotar, Hooktusk, Call on Stand and stuff like that. And the Drake is also vulnerable against mage and hunter secrets that can negate or kill it on the spot when played.
So yes, when it works, the combo is neat but then again, it is hard to set up and MANY other combo decks that can OTK you are way easier to play.
Think about it leo.
PS: I played games where even after 15 turns with Reno, the correct power never showed up. 25% can take a very long time. Any player that does not kill me after that much time really deserve to get killed by the combo IMHO lol.