While this query will expose the queries that are most blocked, it is somewhat of an guestimate. What shows up from this query is the procedures whose wait times cannot be explained by looking at the total CPU cycles. While this will mostly infer blocking, it doesn’t necessarily guarantee that’s the issue. It can also show procedures that suffer from other wait types (disk, network, clr, parallelism, etc).
,BlockTime = total_elapsed_time - total_worker_time
FROM sys.dm_exec_query_stats qs
CROSS apply sys.dm_exec_sql_text(qs.sql_handle)
ORDER BY total_elapsed_time - total_worker_time DESC