It's a tough one because how will we ever know if he's improved in test matches? His Super rugby form has always been good. The WC was a disaster by him, I can think of 3 crucial errors in 3 very important games he made that are just unacceptable. The intercept against Ireland, the cross-field kick against SA in our half and the kick off to start the semi going out on the full. The latter one basically cost us the match that day if you think about it.
You have to be kidding. Blaming that loss on the kick off going out on the full? That's one of the sillier things I've read recently, and there's mudskipper to compete with. Actually, Quade was, sadly, one our better players on the park that day. If I recall correctly, his only other error in the game was a knock on early on. Other than that he played well behind a beaten pack.
The intercept in the Ireland game (if you are referring to the one about 5m from their line) was hardly crucial either, we were chasing the game well before then and our forwards had been utterly smashed. It was a poor decision, but to say it was crucial for the match is, again, silly. I don't see how you can blame just one back for that loss when the forwards are smashed so badly at ruck time and in the scrum.
There's no denying Quade wasn't that good in the WC, but to give that as the reason not to select an inform player is stretching it. If having some bad WC performances meant that you shouldn't get selected again, then Vickerman never would've never made the team again after 2007.