Are classes more interesting in newer expansions?
I am playing on Icecrown currently and the boomkin doesn't seem particularly interesting (mechanically wise) in PvP: keep your buffs and DoTs up, use starfall whenever possible, cast Starfall/Wrath depending on the type of Eclipse you are in. If you get jumped: Bark Skin -> Cyclone -> Heal. I could be doing things wrong, but I have heard about other things how some specs have very easy damage rotations too (arcane mage).
Anyway, I've seen MoP, WoD and the upcoming Legion have quite cool mechanics for many specs (shadow priests O:). Even tho the balance might not be very good with hybrids being out of control and melees wrecking faces (I prefer casters) I would very much enjoy something more in depth.
Am I missing things or are specs more mechanically complicated in newer expansions compared to wrath? And please don't be biased that WotLK is still the best just because you enjoy it more. I wanna know things as objectively as possible.