You've covered most of the basics, really. Skull is usually first kill target (because skull = death), X is usually second kill target (because red X also suggests death/elimination), and mages have taken over moon as the sheep symbol even though that clearly doesn't make any sense whatsoever because druids are the much better match for moon.
I've also noticed that warlocks tend to get the orange circle (also known as the condom or the nipple), and retribution paladins tend to get the star for Repentance. It's totally possible those are just oddities in my guild and raid, but it always seemed like a foregone conclusion when it came up. "Yeah, of course you're the star, what else would you be?"
You nailed it on the head in your question: The right answer is to just explain what you want people to do so there's minimal confusion.
Why are warlocks tolerated? They obviously consort with demons and should be considered members of the Burning Legion. What are the lore reasons why players, and so many player races, are allowed to play a quasi-evil class?
In many cases they're not tolerated at all -- they're just sneaky. Humans have warlocks, but the warlocks as an organization are hidden away beneath an otherwise completely normal tavern in Stormwind. They've evaded widespread notice. If I'm remembering correctly, warlocks even have a class-unique quest to assassinate a noble who is too close to discovering them. By the time a warlock is openly discovered, he's usually one of us -- badass heroes saving the world. Are you going to be the guy who says the warlock that helped destroy the Lich King needs to be hanged? Hell, no. Nobody is going to mess with the guys who axed the Lich King. We are politically untouchable.
Being a warlock is absolutely not encouraged in Azeroth, but the warlocks themselves consider their art a necessary evil ... and their current influence in the world suggests that it's absolutely true. Demons are a problem and warlocks fight fire with fire. They hide away in the cracks of society until they're powerful enough that nobody can deny them.
Is there a good site to get a list of all the different types of CC for each class?
Have questions about the
World of Warcraft? The WoW Insider crew is here with The Queue, our daily Q&A column. Leave your questions in the comments, and we'll do our best to answer 'em!