That would seriously have to be the most ridiculous DRS decision to ever be overruled. To say that the ball hit Morgan's bat off that hot spot 'evidence' is just beyond laughable...
I'm trying to find this on Youtube or somewhere. Going by the Cricinfo commentary, I would say that Clarke was hard done by, but the incident has brought up an alarming issue with how HotSpot is used. Two quick wickets with England at 171/4 and only one more recognised batsman would have made for an intriguing ball-game.
Mike's right about the Aussies needing more runs, though. You could argue that England would have still comfortably chased the target even if Morgan went out second ball, but the gap between the batting lineups and scoring rates was clear. England were cantering along, starkly contrasting the drudgery in the Australian middle-overs; that said, George Bailey ultimately did alright, but that middle period really hurt them. When I went to bed at the end of the first innings, I thought that England would be able to chase the target quite comfortably, if they played as they did on Friday. The cast differed slightly, but the plot remained the same.
