Haven't you heard of cases of people dying form an adrenaline overdose? I must agree though being granted wings shouldn't damage you. Especially ones called mighty wings. But neither should they grant you an attack bonus. What's he going to do slap someone with his new fancy wings? Instead I think the creature should gain the dive ability.
Yes, adrenaline overdose would make sense if the card is called "Adrenaline Overdose", but if you call the card "Rage" or "Berserk", I don't think anyone would assume that it would do damage to the creature or even kill it.
You can make up all kinds of crazy explanations why a card does what it does, but why not just name it so that when a person reads the card, he can almost guess what it does? Lets take "Steal" as an example of good card name. It's pretty easy to guess that this card will take something from your opponent and give it to you.
"Mighty Wings" just doesn't make sense because 99% of people would assume that it gives the creature a "Flying" ability, but since there is nothing like that in this game, why call it "Mighty Wings"? Why not call it something else?