Exploit is on the simple side and I dont mind a few mechanics that have a smaller range of decision making considering the continued complexity creep found in Magic
For example, if you control Johann, Apprentice Sorcerer ("Once each turn, you may cast an instant or sorcery spell from the top of your library.") and Questing Druid is on top of your library, you can cast Seek the Beast, but not Questing Druid
Some of Jace's competition, on the other hand, has been more long-lastingespecially Emrakul, the Aeons Torn, which, a full 15 years after it was first released, is still the biggest, baddest, most broken creature that Magic has ever produced, as a 15/15 flyer that annihilates your opponent's board when it attacks and gives you an extra turn when you cast it
I may be on board with spending extra for a box thats prettier that you like it as long as its equally as protective, but Id never recommend spending less for the same reason