Power BI Performance Issues - Am I missing something?

Hi there,

Im creating a Power BI report with a number of matrixes in it. The main table we are working from in our data model has ~7.5m rows, with 2 dimensions (3 including time), the matrix contains columns of actuals, with a switch measure which adjusts a chosen comparator (prior year values, budget) and a % variance to this value.

We're seeing some serious performance issues when trying to load the matrix we need to show in power bi, and in the online version it exceeds the memory limit. Are we just trying to do too much with Power BI? Or is there something we can do to improve performance? 

Any suggestions welcome!