Having to picking a specific character to beat nest is bad design, or at least greedy design. It forces players to buy certain characters in order to win. I understanding making certain characters better against other certain teams but the EF issue goes far beyond that. Anytime you have a team that removes TM, (Vader or Ventress as lead) EF becomes nearly invincible. Or, if your team has stun with basic ability. Some people invest a lot into one or two specific teams because they can't afford to buy and mod every char in this game. And, not everyone has been playing this game for years. Yes, haters, jump on me and defend the poor devs who have to get paid to make the game. I am a product manager and probably understand better than most how a tech business works. EA probably has to pay an f ton in royalties to Disney. My point is the infinite loop that CAN occur with the EF character. GOH purports to avoid infinite loops in the game -- and EF can get into an infinite loop.
All of you who righteously claim that you can bean EF easily are blind to the perspectives of other players in the game with different, more limited character sets. Yes, you're a great player, you figured out EF's weakness, good for you - stick a gold star on your hand. But, when an arena squad can destroy the other 4 characters in an EF squad in less than a min, then spend the next 4 min dealing continual damage to the EF character that never even gets weaker, it is bad design, plain a simple.
I would propose that EF protection up expires after every enemy has completed a turn after it is first triggered, so that EF does not have to take a turn to lose the protection. This also avoids the incentive to keep EF slow (no speed mod), which I have seen can provide an advantage.
Overall, the game has great design; the battle and character development system is one of the best around for this genre. I am only pointing out 1 flaw.