If it's just a judgement call (if I was GM), I'd say "My bad, guys, I screwed that up," and double the XP.
But really, the changes made that fight so nasty that I don't think you can even give it an encounter level. It was just broken that that much extra damage was heaped onto the PCs. So you're out of the "rules" area entirely and it's more negotiating something that everybody can live with.
But really, the changes made that fight so nasty that I don't think you can even give it an encounter level. It was just broken that that much extra damage was heaped onto the PCs. So you're out of the "rules" area entirely and it's more negotiating something that everybody can live with.