Rastakhan's Rumble Guide
Total Deck Rating
I did not connect that Rummaging Kobold could actually get you multiple Kingsbane. Not sure if that's powerful enough to justify 2-of, since you're running Shinyfinder and only have so many buffs. 1-of might be fine.
Was there any clarification on how Doomerang works with Kingsbane? Does the deathrattle trigger and shuffle into the deck, or does it return to hand? If it returns to hand, does it keep enchants? It's not clear if keeping enchants is tied to the deathrattle or is just a passive effect
I'm pretty sure Doomerang gives you a buffed copy in your hand and not in your deck as they have confirmed that the deathrattle and it maintaining buffs are not tied together.
According to Peter Whalen on Twitter, Doomerang does give you the buffed Kingsbane back in your hand, but Rummaging Kobold will not.