Durant is supposed to be the most consistent one. Klay is boom or bust. Curry is somewhere in the middle.
That's how I see it too.
I think the teams that have no chance to defend the Warriors' offense are the ones:
1) without a couple of decent (edit: very good) wing defenders (for Durant)
2) where there is that one guy that will refuse to switch, lose track of his guy or take plays off in defense. That's when GSW will move until Curry is even slightly open and they'll find him.
There are actually a number of teams that I don't see defending that. Westbrook, Harden and Lebron give you this effort deficit in defense :D. Lebron these days is the King of pointing fingers to where guys should be while staying completely still in defense. He knows exactly how he should defend, obviously, but he doesn't think it's worth wasting his energy switching, closing out and chasing guys around screens.
Thankfully the Raptors are not in this situation. Their players all seem willing to switch and actively defend, even JV even if he's not really able to :D. And they have a couple of guys to throw at Durant.