or maybe just a half decent draw.
true, but the so called big 4 (including nadal there) pretty much get to at least the QF (usually SF) of every slam. in that mix there are also dangerous top 10 players like del potro, tsonga or berdych who can give a big challenge to any of the big 4 in the QF. this is usually the case in every GS.
Even murray, the player who arguably has had the easiest way to a GS in years, needed to take out federer in the SF and now will have to dispute the title against djokovic. that's as "easy" as it might get for a top 4 with a "half decent draw".