He has been disappointing to be honest.
ENG tour, more or less meet my expectation; in NZ, he had very little scope to do with that batting effort & crucial catches going down at critical moment (not for his bowling only - on that wicket PAK dropped the man at the start of his innings, batting 40+ overs against new ball there after), but AUS has been disappointing. Definitely he is not the bowler 6 years back, but I expected better. Those who are trying to sell that his early success are entirely on green wickets doesn't know that he has 5for at MCG & he didn't play that SCG Test on a green top. In 2010 summer, at least 8 other English & AUS pacers played same Test he played & bowled to far inferior batsmen with far, far better catching unit - one can check that summer's Test bowling figures for all.
Coming to his current form, I actually don't think that he is bowling short or wide deliberately. On 1st Day of SCG, I saw him trying to bring the ball in against Renshaw & Warner, which ended slanting down leg. Normally, what happens is Asian Fast bowlers land in AUS & get excited with the bounce of the track - they start to bowl short. By the time they adjust somewhat, it's 3rd Test. In that 1976 Series Imran went for 115/0 in around 20 overs at MCG - then he had a chat with DK on his bowling length before that SCG Test.
BUT, here I don't think that's is the case, it's opposite - Amir bowled much better at Gabba in 1st Test & gradually faded away. This suggests me that he is not full fit, & running short of steam. He has missed 6 years of cricket, hence is faking fitness to play as much as possible. At the moment, probably a semi fit Amir is better option for Mickey has than others, hence he is accepting this. Had couple of U25 pacers been taken to AUS, I am sure Arthur would have rested Amir at MCG - now, for him no point replacing Amir with Sohail or Rahat or Imran or Wahab. I said about Yasir, when he was worked for 80+ overs/Test, that he'll fade away for over work-load in near future & his Captain gives a damn about what's coming tomorrow - one can check my sarcastic post on Yasir's strategy - 29 overs/100 overs max, after that he should fake injury - unfortunately, he didn't need to fake. May be sometimes in future, we'll know this as well for Amir. A modern team can't operate with 4 bowlers & 3 pacers, 2 of them over 35 for back to back to back to back to .... Test - that too in AUS. Or I have wasted good part of my time, trying to understand Cricket & cricket in AUS, best place to play the game.
PAK doesn't have much option replacing Amir. But, I would have rested him from the ODI - it doesn't matter much losing 5-0 inside 40 overs of inside 45 overs. I said before the WI series that he should be rested for T20, which technically Arthur did, because he knew Amir doesn't add much value to beat that pathetic WI unit. If Amir plays for Essex this summer, may be only after that one season in County, h'll be ready for such work load. 65 overs/day FC matches are bad jokes which they mock in QA style - it creates false hope for pacers bowling 3 spells for total 13 overs in a day. Amir needs a series of 100 overs/day FC matches, where he'll bowl 23-25 overs in a day, may be at 85% of his physical limit - that'll improve his stamina & stress his ligaments, without tearing it. After that, he should retire from domestics & spend that time relaxing with family, better use of time. Imran kept playing till his late 30s & became No. 1 ranked bowler at 35+, one of the main reason was that he wasted his time last time in PAK domestics in 1979-80 winter. Wasim & Waquar as well - played in total probably less than 20 matches in 1990s ....