Numbers wise they are sub par even with the most on point performance by the player. The main issue I take with my Shaman is an overly clunky routine with abilities that really don't feel as synergistic as other classes, ability pruning missed a whole bunch of still in game thoughtless buttons, talent tiers are the worst of any class.
You can play virtually any other class, use nothing but your mouse and outperform in every situation with half the effort. After Blizz's comment saying Shaman were overpowered and we just didn't know it, I think its safe to say they will remain convoluted. They could have used an overhaul 2 expansions ago, instead its more of the same. Just keep piling on buttons, nerfing buttons, then adding more to compensate, then nerfing, then adding some number increases, etc. The design of the class shows little to no considerstion for ability upgrading, replacing and updating. Add, Nerf, add, Nerf, add, Nerf, buff, add, Nerf.
No changes of substance. So I'm leveling my priest, warrior and Paladin. DPS warrior, healer and tank. I figure one of those will stick. Currently leveling priest as shadow and he's damn fun. Not mind blowing face melt but he feels great to play for a caster. Warrior is good fun, too. I love Arms tho. Prot pally is super fun to level, also. Then again I skipped MoP so I have no comparison other than Cata when my Shaman was my main as Enh.
They can be improved through design with numbers to follow but that doesn't seem like the intent with the class. I love my dual Axe wielding orc maniac but he's going to sit WoW out until a major overhaul hits.
Then again, if you think its fun and feel like you are performing well, go for it. All about preference. I just feel like I'm holding groups back on my shaman. I don't care to be best, I care to be viable, however.