Personally, I beat Boss Battles with Luigi on intense after several tries. I tried the Yoshi Down+A thing, and you can't recover if you fly way out with him. I tried the little Fox trick where you just try and avoid everything and just keep your distance shooting constantly. Definitely didn't work, ESPECIALLY against Raygoon or whatever that little green snake Pokemon thing is. Nothing was working, so I used my man, Luigi. I would just judo-chop them about three times, down+a, up+a, the whole smash, lol no pun intended. Anyway, using him and his excellent recovery I would just blast them and then always own them with Up+B to the face when they were almost dead. I rationed my hearts, too. I would try and go for 4 to 5 battles then use a heart, then the last 5 or 4 battles I'd use one. I always saved one for Tabuu... cuz going in there with 58% is just annoying to try and recover.....and half the time I failed was because of not being able to time the STUPID XBOX INSPIRED RED RINGS OF DEATH BUTTERFLY ADDITION that Tabuu would do and then do a second time if he had a slap to the face worth of life left and you tried to just chop him.
Did any of you notice that on Intense, when you get to the last two or three battles, the bosses would speed up insanely fast?