No, of course it isn't- which is why the plan should be everybody else gets 30s and 40s, one person makes a bigger score and Clarke makes 100+. Of course it's unsustainable and with an approach like that we'll lose 2 or 3-1, but right now it really is the best we have to offer.
Anyway, we're not as fragile as India or Sri Lanka might be. We don't go all to pieces at the first sign of lateral movement or bounce as those two batting orders have done in recent years, so an England walkover over our batting order isn't a given. I think reports of "6 Australian walking wickets plus Clarke" are a bit exaggerated. Yes, they aren't a patch on our predecessors, but the only genuinely weak players in there are Watson and Hughes. The rest of the top 7 at the least can perform on occasion. I'll try to make an objective analysis of our likely top 7:
Cowan- occupies the crease fairly well, but rarely scores above 50. He can protect the middle order reasonably well from the new ball, but not from scoreboard pressure.
Warner- a proper batsman, not just a T20 wonderkid. But he has his Sehwag moments. The bottom line is he's talented and will definitely improve, but right now he's hit-and-miss.
Hughes- Lol.
Watson- Adds 'balance' to the side, but is totally unecessary. Drop him for a specialist bowler or batsman, because he doesn't offer nearly enough in either discipline. Spells of 2/50 and brisk 40s are pretty much the zenith of his talents.
Clarke- The best batsman, by some distance, in the line up, and in brilliant form as well. I expect him to do really well in England, but there may be problems with support.
D. Hussey- He has a great first class record, and also an exceptional record in England, but he's never played test cricket so who knows? Based on his ODI performances, he certainly has a sound head on him and has bags of experience, so I'm leaning towards the position that he'll be a reasonably good addition, but still not quite taking the place of his brother.
Wade- A real step up from Haddin, but he's not a top class batsman. Decent and effective, but not someone you really want to be relying too much.
While I'm at it, I may as well do the bowlers:
Starc/Cummins/Pattinson/Whoever's fit- Each have their own strengths and weaknesses. They're all handy with the bat, but with the ball, Cummins is the most complete. Pattinson can occasionally be indisciplined, and Starc is very much in the Mitchell Johnson mould. Starc excels when there's swing to be had, as he pitches the ball up, but if there's no swing then they are just treated as half-volleys. Their common problems are staying fit and lack of experience, both playing in England and playing against top batsmen. Pattinson, for instance, has only really played well against India's declining batsmen and New Zealand's poor batsmen.
Johnson- Ouch. He has a reputation in England of being rubbish, which isn't all that far from the truth, but he can on occasion do a reasonable job. I'd still be happier if he were left out of the squad, though.
Lyon- Not really all that good, picks up most of his wickets from mistimed slogs. But at least he keeps it tight. And, on the plus side, we don't necessarily need a world class spinner to succeed in England.
Siddle- A good bowler, who's hardworking, reliable and economical. He's nothing special, but he gets the job done with a minimum of fuss. While landing the ball outside off stump on a good length may be unspectacular, it gets results.