Well, there’s no need to guess since here’s the link: 22.2 Known Issues
“[Added 2/8] We are investigating reports that the Honor Event ended early yesterday.”
“We are also aware that the the Alterac Valley event rewards have ended prematurely for people who have not yet completed their Honor Track. We are investigating the issue at this time.”
A quick fix seems obvious to me - look at the honor, look at what the cards people have, do a database update or whatever that restores the quest to people at the right level (based on the cards from the chain in the collection) with the right amount of honor in progress for that level (based on the tracked value from the achievement). Why they won’t just do that as a triage measure and then get back to their investigating, I don’t know. The clock is ticking on getting to the end.