I agree with sussex here. It's clear if you're actually watching the spells. Anderson and Broad are generally (day 1 Adelaide excepted) bowling well, putting the ball in the right areas, beating the bat, creating pressure, and as a result aren't going for many runs. But the Aussies are reigning themselves in rather than going after them (have you seen the run rates in this series? Warner scored a 16 of 60 balls
). They know that these guys are good with the new ball, but not so good that they can always break through a player being watchful and defending when the conditions aren't helping. So what do they do? Dig in, see off the new ball, and wait until conditions are less favourable and more importantly, the b string comes on - Woakes, Ball and Ali have been very undercooked (if you think Anderson isn't great when conditions aren't helpful, just look at Woakes - utterly toothless, but without Anderson's control), they know they will get bad deliveries they can score off. It's not rocket science.
That said, the Aussies have done well, especially Warner, to play Anderson and Broad the way they have. It's against their instincts.
Re: Cook, I don't think it's a coincidence that his best period in the game, when he scored lots of big hundreds, was when Gooch was batting coach. Since he departed, he's still been a decent opener, but the hundreds, especially the big daddy hundreds, have come along much less frequently.
I'm not a betting man, but if I were I'd be dropping a few bucks on Cook calling it a day by the end of the series. It doesn't look good for him.