Dimension lookups and updates are row-by-row operations; therefore you must create appropriate indexes for getting the best performance. One of the tips that you can follow is creating dimension’s table clustered index on the business key instead of surrogate key. And if you need to do better you can include the current indicator flag for end date as the second column in the Type-2 dimensions. Keep it in your mind that Index optimization must be balanced between the ETL and the query usage. Although you can put the data into staging table and later establish an inner join between it and the dimension for updating the rows that are exists in the stage table. Finally, you must truncate the stage table.
Be cautious about using this method, because in most situations it is not a good idea to put surrogate key away, and index the business keys, for joining between fact-tables and dimension tables are based on surrogate keys.