You exile Experimental Overload even if you don't return a card to your hand
The +1/+1 and haste will make it better than Fires of Yavimaya, and the additional options of Threaten or make a quintet of 4/4 Dragons are both really strong abilities too
The basic mono-colored ones and their new card upgrades are given to you as you complete the Color Challenges, and then you unlock the dual-colored starter decks by completing daily quests, daily/weekly wins, and leveling up
When you learn how to perform this technique of shuffling cards without errors, it will look quite impressive and also ensure the fairness of the shuffle and the randomness of the chosen cards
I will quote the relevant third part about the playtesting: Step Three: Full-Time Playtesting At Creatures, theres a special room dedicated to testing the card game
We now give these batches a name, which you can see with things like historic, outlaws, or modified