Define "barely offering a whimper" ?
When he first came on to the scene he clearly had deficiencies in his technique against an outswinging ball, hence why his averaged dropped a little. Has corrected this flaw and is a lot better off now that he was dropped back when he was so young. However, now there is no reason for him not to be in the team
He scored two pretty spectacular hundreds when he was first selected and then was found out pretty quickly. Hughes was then picked again in the 2010-11 Ashes and did very little. He went to Sri Lanka after that and managed a hundred (his third and so far final of his career) in the third test of that series. He managed 80-odd against SA IIRC in that game Cummins took 6 on debut, and then did nothing against NZ that summer and was dropped. He got called up again last summer to play a fairly hapless Sri Lankan outfit and he managed a few decent scores, but followed it up with a horrific tour of India and ordinary form in England.
Interestingly Hughes averages 54 in the Sheffield Shield, but ultimately this is irrelevant if he can't go some way toward backing this up in the test arena.
By the way your comments about Smith above are interesting. It's also funny how you use Bailey's FC record to deride his test selection but at the same time talk up Shaun Marsh.