i don't really care what level my Pokemon are at. i beat the Elite Four with a level 65 Charizard. the five other Pokemon in my party were at a max of level 26 lol. i had tons of revives and other items. so it was pretty easy. you could say i'm lazy for not leveling up an equal team, but then i'll just say you're right ;D
but after i got the plates and shiz i started running through the E4 with my Mewtwo and Charizard, while Exp Sharing other Pokemon to help my Pokedex =D