I have a Asus G501J. With just Firefox running and a YouTube video playing on wide screen these are the temps I get:
I'm not sure if these are "normal" but in Windows they are lower than this. I'm starting to think Ubuntu Mate has something to do with it because I had the same problem with another laptop. But I'm not an expect. I'll wait for your response.
Thanks.
EDIT:
I'm using both private drivers for the two video cards, and I'm using the Intel one. This is because I have an external monitor plugged and without the private drivers I don't get a good resolution.