The DMV above just shows averages of what's in the plan cache, not exact executions of each query. That may be good enough, it may not be.
Have a read through this. It's a little out of date, but still valid for SQL 2008
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability