DAX Studio and SQL profiler

Anonymous once the index is sorted, and the SQL query is still slow, start dissecting it in parts.

There are lots of known performance optimization techniques within SQL (one syntax is better than other performance-wise for the same output) that can be used.

If you still have issues, stack-Sql-server  will rescue out, as it did for me many many many times.

One more thing to remember, it might be possible that a native SQL query that runs on SSMS in 3 minutes, PQ might return that query result in more than what SSMS takes. (I don't know why and I struggled with that a lot when I started playing out with large SQL tables). SO in that case, I learnt that the sever-side query needs to be super-optimized in order for PQ to not time out.

Also, you might have a choice to bring the whole SQL table `select * from tbl` and use PQ syntax to manipulate the table (to preserve the PQ Query Folding) which will be even more time consuming (from my experience) and I will advise against it (speaking from my bitter experience).

Is there something else then SQL Profiler to get insight in why refreshing takes so long? - I am not sure but try Fiddler.