As a FYI, I did download Brave Beta just to test it out and I have had zero issues with it.
I don't want to advocate using it, because I understand the need for advertisements.
That said, I have used it for less than 48 hours (I logged in at 7:25 PM two days ago, so ~43 hours). These numbers do startle me, however I am unsure how 'bad' they actually are.
For clarification: I have only visited these forums with this browser, so the numbers are exclusive to this site.