I know which one i would say, but that is obviously biased.
However I have in such threads seen not too few people mention Destruction Warlock. This makes me wonder if there is something that I am missing in my understanding about that spec. What do you have to do as a Destro Warlock in order to min/max?
Anyone who played feral prior to the mangle change or even powershifting will tell you how rediculously easy the spec is to play now.
I hope you're talking about pre-cata feral (mangle was still another debuff there), as cata feral was quite faceroll.
In MoP they introduced DoC, execute and most importantly RPPM trinkets. I'll leave it up to someone who played the old feral to compare the two
I always had the impression that it doesn't really matter what class and spec you play because if you really want to push your character to the limits its all equally difficult to master. Nailing your rotation and pushing high dps/hps/tps is only halfway to mastery.
While we are on the topic of hardest rotation, which has the easiest one?
I'll go first: Assassin Rogue, 4 Buttons spam and gg.
Unholy DK gets my vote for absolute easiest. You have no buffs to keep up, the cooldowns don't change your priority list, and on long fights you can spam one attack to prolong your diseases as long as you want. So it's apply diseases, spam Festering Strike, spend Unholy Runes on Scourge Strike, spam Death Coil to avoid capping, transform your ghoul when the button lights up, use Soul Reaper on cooldown below 35%. That's literally the entire rotation. And enjoy superior utility compared with Frost as well, since your pet has a stun and interrupt.
I'd say Affliction warlocks are hard to master. I've seen a lot of average ones but our current warlock who plays affliction/demo is incredible as affliction. One of the best ones I've ever seen in 6 years of WoW.