Didn't someone say that like 70% of the BvS screens were going to be changed to some other movie the week after it released? That would explain the epic drop (WB hopes).
There is a Sammo Hung movie woth Andy Lau coming it, so there is a little competition over there. And there is a tradional holiday coming up. It's not just a China thing, Hong Kong isn't buying into BvS either, it's dropped by 75% there as well, the shame is that in HK it's taking all the screens from Zootopia which also opened last week.