Weekend BG's will be your big push, as the ques are super short and you get a shitton of exp when you win. Experience from BG's during the week really depend on if you win or not. I want to say I was queing for stuff and averaging a level every 3-4 hrs, but the que times had been fairly terrible so I was farming mobs between ques (Hence the mixed bot setting).
Obv you will level faster by playing on your own (I actually did this a lot during the week or when bg lvling was slow to maintain a somewhat decent set of gear), but it's nice to not have to burn yourself out (I have 4 80's, 3 of which I lvld on my own and fuck I hate questing).
I'd say ban chance with HB is relatively low as they maintain the bot well, has a great warden check system (sometimes it's too good because It will drop me due to internet flickering, etc), and has a great community.
What I did to prevent being seen as a bot was I joined a guild, talked to people in guild/chat/whispers every now and again, kept my gear up-to-date as best as I could, and didn't do the same thing for really long periods of time. If I'd run a mixed bot, I'd farm for a few hrs in one location, then move it to the next -- so as to prevent someone seeing it as a bot.
Keeping to yourself, not updating gear frequently, and doing the same pattern for too long all leads to a higher chance of getting banned.