Between the initial 2.0 story and the 3.0 (Heavensward) story, there is hours upon hours of engaging story from patches 2.1 to 2.55. My advice would be to resub but don't buy the expansion yet and get to level 50 to enjoy that story. Everything that happened between 2.1 and 2.55 is probably why many people praise this game's story so much It's all for lvl 50, so try that.
About classes: WHM is a pretty straight-forward healer. Managing your cooldowns with demanding tanks will sometimes keep you on your toes, but in general, not much is gonna change and you will keep throwing Cures at the tank with the occasional dps in between.
I personally think AST would be a great healer class for you, playing around with the buff cards while keeping everyone alive is a lot more interesting than what WHM does. But to play AST, I think you need to own the expansion and have at least one class at lvl 50..?