Yeah if I have unblockable removal in hand when Jaraxxus appears then you can deal with him. If not, it's GG. He's just way more powerful than other cards of similar rarity/cost.
Actually I was thinking of a different card, the name of which eludes me. 3 mana demon, you play it and it "eats" the two cards to either side of it, gaining their attack/health. I've died twice to decks that use that.
Currently running 8-16 in arenas. Sigh. At least it's a chance to do something different. I chafe at the 9-decks-max restriction since it prevents me from trying lots of whacky things. I would love to have my standard X deck (mage, paladin, hunter, etc) and then fool around with other builds for the same character. I'm leery of dumping my standard X decks because when the quest pops up to win N games I want to just pull out a deck and know how it'll work.
(Of course, this is all because I'm a cheap bastard and don't want to pay cash for Arenas. So I do quests and play games until I have enough gold for an Arena entry. Then I go play my 3-4 games there and am done.)