Drastic performance difference in View Dependencies between SQL Server 2005 and 2008 R2
The 2008r2 "View Dependencies" functionality was completely rewritten from the 2005 version. This is because the 2005 version didn't work.  

So it's not surprising that the results may be different (i.e., they should be correct now).  It is a little unexpected that the 2008r2 version might be slower at it, but not entirely surprising, as it is after all, using a completely different approach.

So, my guess would be that this phenomenon has little or nothing to do with your other problems.