Was able to confirm with an MS PowerBI support engineer that with a premium per user license you are limited to 1 request every 5 minutes for exporting paginated reports. This information can also be found here (I missed it - other articles alluded to a 120 request / minute limit)
The engineer said there are requests in to have this changed. I'm not sure how the expect people to adopt power BI, forcing them to by at least a P1 capacity at $60k/year to export some reports. I can do all of that basically for free with SSRS right now.