First, let me stress again - this is a Gold scenario. It isn't meant to be easy; it seems that most (all?) of our Gold scenarios tend to poke at the corners of policy, which - as in this example - leads to a great deal of disagreement and (hopefully, usually) healthy debate. While our conclusion is Drawing Extra Cards (DEC) and downgrade, I can't be upset with those of you who followed your logic and understanding of policy to get to Game Rule Violation (GRV), or DEC with no downgrade; again, the purpose of Gold scenarios is to make you stretch a bit, “think outside the box”, and with an overarching goal of a better understanding of the philosophy behind policy.
On the confusion about more than one card going into an empty hand - yes, the language refers to a single card, not multiple. By far, most instances of DEC involve a single card. (We never imagined a Knowledge Pool scenario like this, when constructing that language in the IPG!) The philosophy here is simple: it's clear what card(s) were drawn (one was the card still in hand, the other was the land Nathan played), so the option to downgrade and fix things is still available.
About Out of Order Sequencing (OoOS): as others have already noted, you can do things in a technically incorrect order if you still arrive at a legal outcome, and didn't gain advantage by doing so. In this case, Nathan did not arrive at a legal outcome, so OoOS can't apply. Similarly, “the error was not the result of resolving objects on the stack in an incorrect order” was mostly for things like
Horizon Spellbomb, or maybe
Kozilek, Butcher of Truth getting countered and drawing before shuffling, etc. Yes, the correct order of things on the stack (1st Bolt, 1st Trigger, 2nd Bolt, 2nd Trigger on top) seems to have been ignored, but that's not at the root of what happened here. Those clauses are meant to protect someone trying to do things correctly but failing on obscure technicalities (H-Spellbomb is the poster child for that).
If we apply a very precise analysis, we can easily say “oh, well, Nathan failed to discard before the 2nd draw, and he also failed to resolve that 2nd Bolt (evidenced by not changing life totals) before resolving the 1st Trigger's draw, so that's clearly a GRV before the DEC, so…” - but, as noted in George's official conclusion, that takes us too far down a purely analytical path, and ignores the base philosophy: at what point could the opponent have noticed something going wrong? It's only when drawing the 2nd card that the opponent - or any observer - could detect a problem.
Why is Rummaging Goblin (RG) different? Well, part of the answer seems to be “because I'm not making myself clear”. RG has a cost to activate its ability; if you pay part of that cost (tap) but not all of it (discard a card), you've committed a GRV immediately prior to drawing, so DEC doesn't apply. If you fail to pay any of the cost before drawing, you could - again, via a too-fine technical analysis - argue that not paying any of the cost is a GRV. However, once again, the first time an opponent can detect what's wrong is when the card is drawn - not when the cost isn't paid. As others noted, you can't detect something that didn't happen…
As to the deviation, by putting both cards into the graveyard - how is that not
the correct zone? The only zone those cards can correctly be in, is the graveyard. Be careful here - this remedy for DEC with downgrade is
not a rewind. If we were rewinding (because we'd missed the subtleties that make this DEC, and ruled GRV), then one of those cards would end up back on the library, the other in hand, and then Nathan would discard, and … uh-oh, just got messy … decide whether or not to draw & discard for the 1st trigger. But that's all speculative, since this isn't GRV, and we aren't rewinding.
d:^D