Haven't played wow since WotLK,

I haven't played wow in a long time, I've looked in to Catta, Panda, and Wod, but they never really interested me enough to buy the expansions.

Now Legion seems interesting, but I've been away for so long I'm not sure if it's even worth getting a wow expansion any more.

And on top of that, The server I was playing on was basically dead when I left (Alterac Mountains) and I'm kind of worried if I do get the game, it's going to be like paying a monthly payment just to play a "not so good" single player game (Not as good as fall out or something).

So my question, Is Legion worth getting for some one who has not played in a very long time?