Thinking about going back as well.. Want to get a few of my other characters to 85 and pvp or raid.
They brought back the year subscription which seems like a pretty good deal but not sure if i'd even play for a whole year.
World of Warcraft Annual Pass FAQ - Support - Battle.net Support
If you've got a friend that's already playing get them to recruit you. 3x exp up until 80 now.. roll a tank or healer and just run instances all day long and you'll hit it in no time.
When it was 3x to 60, it took my friend and I a couple of days doing instanes and questing to hit 60.