He should have known that sidelining 2 of the greatest batsmen at the same time, that too against a stronger team, away, would have some repercussions. Ponting & M.Hussey were the backbones of this Aussie batting lineup for such a long time. Its going to take a long time to find 2 superstars, which is a slow process.
The Aussies are always ambitious & capable but lack of able personnel is taking its toll, maybe for the time being. Its their rebuilding process & Arthur has joined them at the wrong time, when things are unstable & winning isn't that regular.
Maybe similar to Kirsten's & D.Fletcher's coaching reigns with team India. Both have had similar teams but success graphs are the exact opposite. With couple of very important players missing or out of form, Fletcher has had to endure big torture, whereas Kirsten just moved on in the nick of time, to save his reputation.
Now Arthur might have to endure bit of embarrassment , where he won't know, why the most successful Aussie team he joined as the coach, goes missing in the face of hostility from a better team, i.e. England. By the time Ashes happens, they would either go flat out, in ultra attacking mode or would crumble, like the English teams used to, with great set of Aussie players, which are more evident in English side, as of now..