Shadow Priest vs Warlock: In my opinion and experience, Shadow Priest is "easier" to play than two out of three of the Warlock specializations.
Here's a scraped walkthrough of the four specializations:
Shadow Priest: Maintain two debuffs (Shadow Word: Pain, Vampiric Touch), use Mind Blast when possible, use Mind Flay when Mind Blast is on cooldown. Only use Mind Spike if you get a talent proc (if you have that talent). At three Shadow Orbs, use Devouring Plague. If the target is below 20%, use Shadow Word: Death (possibly replaces Mind Blast).
Destruction Warlock: Maintain one debuff (Immolate), maintain one self-buff (Backdraft) with Conflagrate and spam Incinerate. Use Chaos Bolt when you have a Burning Ember. If the target is below 20% health, Shadowburn replaces Chaos Bolt.
Affliction Warlock: Maintain three debuffs (Unstable Affliction, Corruption, Agony) and spam Malefic Grasp. Use Haunt when you have a Soul Shard (Nightfall allows you to regenerate Soul Shards during combat). If the target is below 20% health, Soul Drain replaces Malefic Grasp.
Demonology Warlock: Maintain two debuffs (Corruption, Doom) and spam Shadow Bolt. Use Soul Fire when Molten Core procs. Use Metamorphosis when you are at maximum Demonic Fury. If the target is below 20% health, Soul Fire replaces Shadow Bolt.
Destruction is arguably easier than Shadow Priest and the two other Warlock specializations. Shadow Priest is arguably easier than the two other Warlock specializations. Demonology, in my experience, is definitely the least easy specialization to play, primarily because you have to switch in and out of Metamorphosis all the time to keep your Demonic Fury below max.
As for rouge and Feral Druids, rouge is overpowdered, but the Rogue is a pretty balanced class. I'll leave it up to some of the resident Rogues to answer that question, since my own Rogue never got past level 60 (stopped playing it when Ferals were revamped). I do believe I can answer whether or not Feral Druids are easy to play, though.
If you compare the Feral Druid to the Shadow Priest and Warlock specializations above, I'd place the Feral Druid between the Demonology Warlock and Shadow Priest in terms of skill level. Boiled down, you have to maintain three debuffs (Weakened Armor, Rip, Rake), maintain one self-buff (Savage Roar) and spam Shred/Mangle. If the target is below 20% health, Ferocious Bite replaces Rip (since it refreshes Rip).
All three classes (Warlock, Priest, Druid) are classes that are easy to learn, but difficult to master. While the above priority lists might net you anywhere from 50-80% of your maximum potential DPS, to achieve the maximum, you have to do a lot more stuff. All three classes utilize manually applied DoTs to some extent (unlike the Warrior, for instance, who applies DoTs automatically), so you have to be on top of your DoT duration and constantly factor it into your calculations. Can you squeeze in one more Malefic Grasp, Shadow Bolt, Incinerate, Mind Blast or Shred before your DoT drops? If you can, it's a DPS boost; if you can't, it's a DPS loss.
In my opinion, you should look at the classes and decide based on which class and specialization you think is more interesting.
Do you want shapeshifting, healing and melee combat? Feral Druid might be your thing.
Do you want demonic pets, shapeshifting and a mix of melee and ranged combat? Give the Demonology Warlock a try
Do you want demonic pets, fire spells and ranged combat? Destruction Warlock is probably up your alley.
Do you want demonic pets, debuffs, drains and ranged combat? Try out the Affliction Warlock.
Do you want healing and ranged combat? Take a look at Shadow Priest.
Note: Affliction and Destruction Warlocks currently achieve maximum DPS by not using their pets (sacrifice them through a talent). This may, however, change later on.
Edited, Sep 12th 2012 4:37pm by Mazra
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