Umm... I'm sorry, but I really can't read, "As Ishgard doesn't want to repent," as an indication that it's all about past sins. Not wanting to repent = still doing the bad things. In other words, reiterating the whole "they're about to sin again" deal and putting that as the immediate cause for retribution. (Since it appears they might be willing to delay it if the Ishgardians weren't about to do Bad Things again...)
My opinion on the whole is... I wouldn't mind the English version that much if it wasn't for the fact that it seems to be the only language that takes that path. Haven't seen any direct translations of the French and German versions, admittedly, and I don't know the languages nearly well enough to attempt to understand it directly, so if any of you players who do know those languages would be kind enough to help with that it would be awesome indeed. But from the comments I've seen in this thread, French and German versions seem to be following the Japanese text a lot better.
And yes, the impression I got was pretty much a, "Fine, Mama Crystal likes you despite you being a tiny ant, so I won't kill you -- but I'll stand by and laugh if someone else does (say, a dragon maybe? *innocent leer*). And I'll make sure you can't cheat by drawing on Her powers, either."
Even after reading through the English dialogue after seeing the more directly translated version, I still get the image of Midgardsormr grudgingly agreeing to uphold some pact he and Hydaelyn seem to have. And that he clearly doesn't really like her either. (I mean... "trickery is thy shield"? He's pretty much calling Hydaelyn 'trickery', since she's the one shielding us.)