It is not just google dance, It is Google Lap Dance. Google is trying to personalize its search result pages.
judt leave it be. time will heal. maybe changing meta tags is just like changing url so people need to reindex and re-do the math again lol. it takes time.
Was it a very new website ? it must have seen initial boost or hotness factor and now have sunked in its real position.
I suffered the same problem. My site was in top 10 for months for various keywords, now it's in page 4-5 for the same ones. Maybe something's wrong with Google algo!
same thing happening with my websites too ... and they are few years old website, haven't changed the meta, backlinks are proper .. but still my serp went down from top 10th position to 60's & 70's position