Azure SQL DMV procedures slow

Question

I tried to use Azure SQL Performance metrics and for me they are running very slow and consume lots of CPU (up 100%).

Example takes 4 minutes to execute, CPU 100%

SELECT * FROM sys.resource_stats WHERE database_name = 'db1' AND start_time > DATEADD(day, -7, GETDATE())

Example instant, CPU 80%

SELECT end_time, avg_cpu_percent FROM sys.dm_db_resource_stats 

I want to monitor DB as often as possible, but these monitoring queries kill all statistics.

1. Any ideas why it might take so long?
2. Are there any other ways to get stats from Azure SQL?