Compelling content for a small group
Raiding isn't everyone's thing. LFR definitely isn't appealing to everyone. But most of us, at some time or another, run 5-man content. I cut my teeth on BC heroics with a consistent group and had a blast. Challenge modes are the natural progression of those, as well as Cataclysm heroics (which were a bit too hard for the average pug in many cases). If you like to get a few of your friends together and tackle difficult content, CMs are the perfect opportunity to do so.
Content that remains relevant
Although to a certain extent improved gear and class changes have made CMs somewhat easier than they were at the very beginning of the expansion, this is content you can't just outgear. You can't waltz in and steamroll it due to the gear scaling mechanics. I'm not sure how this will carry over after a new expansion, but right now they are still a very respectable challenge.
Accessible to most players
I've seen a few people sounding a bit down about CMs, assuming they were out of their personal reach. Blizzard has said that they expect the average player to be able to achieve bronze in all of the CMs. I'd say that's fair, and with a little preparation, you can attain silvers. If you're willing to really work for it, you can aim for golds. But don't feel as if CMs in general are something you can't do or they're "not for you." You might find that if you get a group together and start doing them you can go further than you thought!
If you're someone who needs a carrot, or like me you are very transmog motivated, there are some convincing reasons to set up a group and tackle CMs together.
Challenge Conqueror: Bronze rewards you with a cool account-wide title, "The Undaunted."
Challenge Conqueror: Silver rewards you with your choice of one of four unique phoenix mounts: Crimson Pandaren Phoenix, Ashen Pandaren Phoenix, Emerald Pandaren Phoenix, or Violet Pandaren Phoenix (pictured above). There's no wrong choice, and CMs are the only way to obtain them. The phoenix is only usable by the character that earned it.
Challenge Conqueror: Gold rewards the best thing - a set of transmoggable gear that is unique to your class and has special animations. The Elemental Triad Regalia projects a version of the Kirin Tor eye above your head and sometimes shoulders when you are casting a spell. What's fun about it is that it also considers things like "sitting" to be a spell, so if you sit down you get a constant eye projecting over your head. If anyone asks, just tell them you're thinking really hard.
Mages in challenge modes
I saved the best news for last. Mages are extremely strong in challenge modes, specifically frost mages. Some of you may hate hearing this, but frost is pretty much a requirement if you're going to be pushing for golds. I don't know any mages who did gold CMs as either fire or arcane. Both fire and arcane rely too heavily on gear scaling (crit and mastery respectively) to excel in an environment where gear is scaled down. Frost, on the other hand, performs very well at low gear levels. If you just want to give CMs a shot casually and don't intend to work towards golds - do it as any spec you like.
If you're pushing further, though, you do need to learn frost if you don't already know how to play it. The good news is that once you have it down pat, we have so much to offer a CM group. We've got flexible CC, we're very durable and survivable, frost has a boatload of AoE DPS and our usual mage utility, of course. For the rest of the article, I am going to assume that you're playing as frost.
Now you've decided you're going to give challenge modes a try. You have put a group together and it's time for you to get yourself ready. Where do you start?
Talents & Glyphs
The best thing about CMs is that many of these choices are completely personal. They may change depending on your group composition and your strengths. So don't take any advice here as written in stone. The best choice for one mage may not be best for another.
Tier 1 Choices: Presence of Mind, Blazing Speed, Ice Floes
I used Ice Floes because I know that I really suffer when I don't have an easy way to cast while moving. Blazing Speed is also a strong contender. Ways to move quickly can be invaluable in CMs, and Blazing Speed is not on the GCD so you can use it to quickly zoom out of something if need be.
Tier 2 Choices: Temporal Shield, Flameglow, Ice Barrier
Ice Barrier and Temporal Shield are both strong choices here. It depends somewhat on you. Temporal Shield is also not on the GCD and can be used even while stunned, feared, etc. If you're good at timing when best to use it, this might be your best option. Ice Barrier is good for its ability to prevent any spellcasting delay.
Tier 3 Choices: Ring of Frost, Ice Ward, Frostjaw
You could make an argument for using any of these and it will vary depending on the challenge mode. Ring of Frost probably has the broadest application, if only because the tank can see visually where it is and lead mobs into it. Ice Ward can be situationally useful - remember that when a mob is rooted, it will turn and smack whoever is closest to it (sorry, melee buddies). So if you're going to use Ice Ward make sure you've checked with your tank and group that it's what they'd prefer.
Tier 4 Choices: Greater Invisibility, Cauterize, Cold Snap
Your choice here is actually going to depend on a few factors.
1) Are you doing a CM where invisibility potions are used?
2) Are you going to use invisibility potions or are you going to use your own invisibility?
There's no right or wrong answer. If you use your own invisibility, you can use a DPS potion as often as you like. The cool down triggered by an invisibility pot is really long. So you'll definitely do more DPS this way. But you make yourself a bit more vulnerable at other times. Personally I (and my healer) preferred Cauterize and it saved my bacon many times that would've otherwise killed me. Greater invisibility is also an excellent damage reduction cool down and if you're used to using it, by all means use it here.
Tier 5 Choices: Nether Tempest, Living Bomb, Frost Bomb
As everywhere else, Nether Tempest is best for multi-dotting in AoE situations, and Living Bomb is strongest on single targets. Frost Bomb is best for if you are going to have 6+ things stacked up, so your choice here may depend on how aggressively your group is going to be pulling.
Tier 6 Choices: Invocation, Rune of Power, Incanter's Ward
Invocation is the strongest choice in this tier. You're going to be moving too quickly to want to place a Rune of Power again and again. Incanter's Ward could be workable if you learn all the best places to use it so you're guaranteed to reap the benefits.
We have fairly standard options for frost here. Glyph of Water Elemental is necessary to make your watery friend smarter. I'd highly recommend Glyph of Splitting Ice; the cleave is incredible and very necessary on large AoE packs.
For your last glyph you have a bit more choice. Glyph of Cone of Cold is pretty compelling for its 200% increased damage on a spell that's a key component of your AoE rotation. In my opinion this is the best choice for your third glyph. Glyph of Arcane Explosion can help you reach more trash without having to reposition quite as much. The other glyphs provide lesser, often situational benefits but might be worth considering. Take your pick from: Glyph of Evocation, Glyph of Rapid Displacement, or Glyph of Blink. After everything above, this is what a sample build might look like.
Our next installment will dive right into gearing, gemming, some useful macros and general frost gameplay in a CM situation.