Or is there no place for that?

The beta forums (if you were invited, there's a link in your invite mail)

If you got the key off Curse.com, then you have to use in game report tools as the keys don't come with Beta forum access.

However, if it's like the last beta, a survey will be sent out to everyone allowing you to provided extensive feedback.

Your beta invite should have a link to the beta forums. There is also an ingame feedback option and bug report

if you are in the beta (stress test weekend) type /feedback inside the game and provide it.

that what most GM saying the /feedback is your friend.

Please check your invite e-mail.