I would have personally kept the use creature objective as a '100% cast chance' of creature in the deck. This would have been far cleaner than just starting a match with the said creature. Allows for more bluffing as you could choose to then cast a regular chance cast card of the creature and keep your opponents guessing which is which.
I think it would be better all round if your opponent didn't know which creature you were trying to kill them with. With the current system all you need to do is target whatever creature starts on the maps with a magic attack and it's potentially game over on turn 1.