Plus, all they really need with a sableye start is a collector. They'll search out crobat and unown dark. It's very unlikely that you'll be able to start out with 2 of your 4 tombs when you need to.
Well, yes, but keep in mind, the odds of an opponent having both a Collector and the Sableye to start first are only slightly better than having double Tomb.
That said, Nance's criticism is legit, IMO. I keep forgetting about the mulligan rule, sadly.:nonono: