Sky went into the Vuelta convinced Wiggins was going to top their GC. Do not fault them for this, no one else saw Froome coming so it wouldn't surprise me if his own team didn't. Their failure though was not recognising soon enough that Froome was their best option. Strategically, the call was never made to save Froome from working for Wiggins. It was a heat of the moment decision on Angliru, Stage 15, where Brad was dropping off and Froome stayed with him, only for Wiggins to relinquish leadership on the spot and allow Froome to go again. Had Sky made the call to move to dual leadership, there's a reasonable chance that Froome would be a GT winner now.
It would be silly for Sky not to learn from this and approach the Tour the same way they did the Vuelta and convince themselves that only one of Froome/Wiggins will be their GC contender. If they are still both in contention, look to make the call after La Toussuire. If they are still inseparable, try and turn that into an advantage not a weakness.