Slow performance

Hi,

I have created a Power BI report and have noticed something odd with my reports, Let me explain a little about this report, I've created a report with four datasets and connected these datasets, when I create visuals they take roughly around 30-40 secs to display results on the visuals. Later I identified a single view which had the exact same columns needed for these reports and switched the query and merged three datasets into a single dataset and connected the datasets, now I had just two datasets, with this I hoped that the reports would be faster in displaying results but on the contrary, these visuals now take over 7-8 mins to run, it's insanely slow and I don't understand the reason what's causing this to happen. 

Also, I do not have any calculated columns or measures, the datasets are in Direct Query mode and hence no transformations on any of them, the datasets are connected as one-to-many with a single filter. There are many other reports that I have built over the months the exact same way and never have I ever seen any sought of performance issues on those reports. I use the exact same query on SSRS and the report works perfectly fine. 

I would really appreciate it if there are any suggestions/tips/solutions for this issue. Would also like to know if any have faced similar issues before.