I'd have to guess that it's bad luck. When this deck was created, there was no Butterfly Effect, no Neurotoxin, no Spine Carapace, and Skull Buckler was different -- but those are about the only things that have really changed.
If you're really having that big of a problem, I'd suggest switching the Mark to :darknessmark and swapping in some Steals -- OR switching the mark to :lightmark and swapping in some Sanctuaries. Both of those mods make the deck slightly more likely to deck out, but slightly more flexible in the number of threats it can stand up to. By and large, though, given the amount of positive commentary, I think it's likely that it's just a rather unlikely streak of bad luck.
Good luck going forward with this!