There seems to be an issue as of the latest patch (deployed earlier this evening (11/03/13)). It seems to have caused an error with the way that Rushing Jade Wind interacts with Spinning Crane Kick, at least with the damage multiplier caused by RJW, causing Spinning Crane Kick to hit for impossibly high numbers (I was getting 13-14M crits in LFR).
With heroic progression coming tomorrow and Wednesday for US and EU respectively me and several other people who noticed this bug thought it would be appropriate to post this in as many places as possible to stop this being abused to beat heroic-modes.
It's very hard for me to resist not going and doing some achievements I'd never be able to get, but I don't want to get banned so yes. Play around with it if anything. It works in PVP too by the way, at least in a /duel.
Same, but playing around a bit in solo/5mans shouldn't be too harmful.
This is huge exploiting potential and needs immediate attention.
Given how previous 'over the top' damage bugs have been treated we can expect a couple of hours before the hotfix. It's just the % modifier on RJW that's bugged.
I can see them issuing rollbacks on progress made in raids using this skill. But I doubt they'll banhammer people using it to farm the odd heroic or gank some guards in the opposing faction city. (That would be a third of the monk playerbase pretty much, even tho Xuen might win out on the populatiry poll).