Ironically it was a missing index that caused the bottleneck. But here it is for anyone that might need it.
DECLARE @indexName VARCHAR(128)
DECLARE @tableName VARCHAR(128)
DECLARE [indexes] CURSOR FOR
SELECT [sysindexes].[name] AS [Index],
[sysobjects].[name] AS [Table]
FROM [sysindexes]
INNER JOIN [sysobjects]
ON [sysindexes].[id] = [sysobjects].[id]
WHERE [sysindexes].[name] IS NOT NULL
AND [sysobjects].[type] = 'U'
OPEN [indexes]
FETCH NEXT FROM [indexes] INTO @indexName, @tableName
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT 'DROP INDEX [' + @indexName + '] ON [' + @tableName + ']'
FETCH NEXT FROM [indexes] INTO @indexName, @tableName
END
CLOSE [indexes]
DEALLOCATE [indexes]
Read more: Hatim’s Development Blog