You can't deny it, Swann has been the difference. England haven't been significantly better with the bat, only marginally so; and the Australian fast bowlers have mostly outperformed the English fast bowlers. So where are the results coming from, given that the Australian quicks have made up the difference that the Australian batsmen gave away to the English batmsen? Logically it can only be Swann. Either Swann or fielding.
Australia aren't anywhere near top form, either. The only players that have looked 100% are Harris and Siddle. Clarke is still one gear short of hitting his peak, and the rest (except maybe Steve Smith) are well below their best. This is a far inferior team to the 10/11 English team, as well, so even when everybody peaks, I don't believe they will be as good. Conversely, this is a better Australian team than 10/11. If CA can bin Adelaide and play a test at Hobart instead, then I think Australia have at least a (slightly) greater than 50-50 chance of winning the series.