The rule of thumb is that anything over 10% ready *per vCPU* is bad , so with vCPU you are going to get higher figures , so its nothing to worry too much about.

Jason Boche said it much better than I did

http://www.yellow-bricks.com/2010/01/05/esxtop-valuesthresholds/comment-page-1/#comment-5861

are you actually getting an application performance issues ?