Data warehouse: Can I tell any details from Source System on delays or blocks?
Okay, I am going to assume that we are talking about ETL operations for loading data into your data warehouse. One great option that you have available to you since you are using SQL Server 2012 is creating a SSIS Catalog and migrate your ETL jobs to be hosted there. This offers you tons of reporting and performance counters that you can use to track and troubleshoot various ETL issues. 

After you identify a baseline it really is performance tuning on your long running ETL's, SQL Server Data Tools shows performance statistics and you can manually run them to see where it it taking the most of your time. Start with the query to the source system and make sure it is tuned properly, then check your lookups and inserts and updates. There are many ways to increase performance of your ETL's. Basically ask for the minimum amount to get done what you need done, make sure you are doing set based operations for your updates as opposed to row based. 

There is much more performance tuning tips depending on what you find by digging into your ETL's.