First, you need a friend who always gets invited to the alpha. You know the one. They have a keychain with 47 beta keys and a t-shirt that says “I was there before it was broken.” Latch onto them. Buy them coffee. Offer to carry their bags in-game.
If you don’t have that friend, become that friend. Start posting detailed feedback on the forums. Use spreadsheets. Cry in public about class balance. Someone at Blizzard will notice. Probably.