I say no...not only because I use them from time to time but there are ways to beat them...yes perhaps they are a bit over powered at times but changing their stats is not the answer, if you dispise uppers so much, then make a deck just to beat the Uppers...but then you will leave yourself open to all the other decks...so I say leave the cards the way they are and play on.
Uppers only have a few good cards(zatman dorian samantha rubie beetenka), but their bonus is the best thats why everyone uses them. (although some clans don't even have that many good cards, like nightmare and since the higher levels got banned in ulu watu they aren't great either) in my experience, when cards get banned usually the clan is weakened (except pussycats)
I am not saying that Uppers are not beatable, but if you play tournament and you try to mix little bit more creative deck (mostly when you cannot afford super power cards), and then you fight each second battle against the pretty much same Uppers deck, it frustrates a lot. Then it is only about luck. I don't have same experience with any other clan, so I would say, that Uppers are really overpowered, maybe not all, but those 5-6 characters (that are even quite ugly
I would say to simply add more Uppers cards to the not allowed in ELO section. Together with the Ulu Watu they're the only 2 clans that have three 8 power cards. But in ulu watu 2 of these are banned from ELO, why not take a 2nd 8 damage card out of the uppers deck as well?