When in doubt, shuffle the deck.
It boils down to optics. Since it's been see that Harper is the biggest micro-manager since CD Howe, it really doesn't mater who's in what portfolio. Any minister in any portfolio is just going to dance the jig the PMO tells them to do. So this makes a shuffle an attempt by Harper to try to get his sagging poll numbers unstuck, and unstuck in an upwards direction. By trying to put a better face on the cabinet he has, it would seem that Harper is trying to pull the wool over the eyes of Canadians yet again. In the words of Sir John A. MacDonald "give me better wood and I'll build you a better cabinet". Moving around the same old rotten lumber is not going to give Harper's government the fresh face it seems to want going into the next election, whenever that will be.
Will it work? Probably not. The last shuffle did the Harper government no good in the polls and there's no reason this new one will either. In fact even Global News which normally paints a rosy picture of the Harper Tories, in an article that almost reads like a desperate plea to Harper, says a shuffle will accomplish nothing. So in absense of any real government from the Harper Tories, its re-shuffle the worn-out deck and hope that re-dealing the same few cards will change things. It won't, of course, but Harper has to try. The alternative is to actually govern which could cause the Tories to be more unpopular and their minority, let alone a majority, will slip away.