I have completed 7/7 of the Artifact Challenges. Here's come general tips/advice on completing them.

Proof: http://ift.tt/2vkhImK's Fall: Completed on BM Hunter and WW MonkThe God-Queen's Fury: Completed on Assassination Rogue and Ret PaladinClosing the Eye: Completed on Survival Hunter and Havoc Demon HunterThwarting the Twins: Completed on Balance Druid, Shadow Priest and Frost MageAn Impossible Foe: Completed on Unholy Death KnightEnd of the Risen Threat: Completed on Holy PaladinThe Highlord's Return: Completed on Protection WarriorAt the time of beating them my rogue was about 910 Heroic night hold geared and my paladin was 910 mythic+ geared. The rest of my characters were around 900ish ilvl with mythic+ and nethershard gear. I recommend at least 900ilvl as a starting point to begin attempting these challenges. Some challenges may require a higher ilvl depending on your spec or recommended legendaries if you are at a lower ilvl. If you have any specific questions on a challenge please ask and I will be more than happy to answer.Do not give up or get discouraged: Guess what, you will die, a lot. Everyone will and everyone has. This is very much a solo raid encounter, you will have growing pains and learning curves. Just because you wipe the first time, second time or even the 50th time doesn’t mean it’s impossible. Keep trying and learning from every wipe, ask yourself why you died and what you could’ve done to prevent it. Don’t put the blame on legendaries or gear. When you finally push to that final phase and your heart is pounding and hands are shaking and you almost have it down, guess what, you will most likely die again, it happens, learn what went wrong get back in there and get it done.Make a strategy that works for you: Not everyone will be on the same level as far as gear, legendaries and skill goes which means strategies could differ in small ways that may or may not have a bigger impact in how you approach your artifact challenge. While some strategies are a little more set in stone (shadow priest) not every strategy will work for you. A good example I can give is the protection warrior challenge. For this fight the legendaries I had were Prydaz and the Hands(dps increase essentially). For me I was able to do more damage and survive in the death and decay longer, and once I figured out that a healing orb would reset my stacks, that is what I started building my strategy around. I would get in as much damage as I could on Variss, surviving for as long as I could, then heroic leap to an orb then do eye management as my stacks started to fall off. I saw many other tanks getting a few stacks then jumping out early and taking care of eyes and taking phase 1 a little slower than me. Now my strat may not work for you (though I do recommend at least trying it) so you may have to come up with something that works for your situation. Be open to try new things to see if they work and constantly question your strategy. Don’t be afraid of wiping an attempt if it means you will get new information.Mastery of your Class: As Blizzard said this is about mastery of your class and if you are sloppy with your rotation and have hesitation when using your abilities you will have a rough time. On survival hunter when I started getting past phase one it would take me about 9-10minutes to get to that point, but as I kept trying and got more comfortable with survival hunter, phase 1 started lasting about 6minutes. Getting better at my rotation and overall feel for the spec made phase 2 much more easier as a result. If you feel like you need more practice with your spec I highly suggest running low difficulty dungeons to get more comfortable with it. Be that heroic/mythic/low mythic+ keys just do a few each day or as many as you have free time and you will see yourself become better and better which will translate into the challenge.Keep focus: Learn to break out of your tunnel vision and ask yourself what needs to be done in this moment. Losing focus will be the cause of 100% of your wipes. Even if you have to pause for a second or two to look at the situation it will help you more than continuing to tunnel. This is honestly a good tip for WoW in general. Anytime you feel yourself starting to tunnel pause and ask yourself what's the best possible thing I can do right now and do it.If possible, record your attempts: It's very helpful to be able to rewatch an attempt. I can't tell you how many times I've noticed myself preforming my rotation poorly or not hitting a proc ability or just flat out failing a mechanic. It's also helpful to see what killed you if you didn't know how you died. Also when you die, before releasing click that recap button to see what killed you, very helpful.Quick Tips for each challenge.Feltotem's Fall: Shortly after the adds spawn he will do his cast. It's ok to focus him until he casts, then interrupt, then go handle adds, the adds don't need to be taken care of right away. The worm will do two Sonic Scream's when he pops out from the ground, it can be very handy to hard interrupt one of these with a CC/Stun, especially if you don't have decent healing. All adds will despawn when transitioning to phase two so you can focus him if he is close to dead.The God-Queen's Fury: Overall do not worry about your dps at all if you have to handle mechanics. The only dps check here is the absorb shield and it's easy to save CDs for. After a while she will eventually flip between absorb shield and valkyrie walls. It's an endurance challenge (more so if your dps is low) so expect a long fight and keep focus.Closing the Eye: Before he transitions to the arcane phase (where all the adds spawn around the room) run to the middle of the room and if you have a CC ability use it as well so he stops casting on you. You can then use a movement speed increase to get to him in half the distance. Survival hunter cheats on this mechanic because harpoon resets every time you kill an image, also for survival send your pet to the next image you go to before going there so you can use your flanking strike right away. Also for survival hunter flare will break him out of the arcane phase. Images that get their cast off will knock you back. If you have a 3 minute 30 second meta on DH you can pop it phase two a little before the boss becomes attack-able and meta will be up towards the very end, very helpful with the leech talent too. The shadow orbs will always come out behind him in phase one so just take a quick second to notice his position and face him and the orbs will be lined up with you. Sometimes they will come out in another direction but it doesn't happen that often.Thwarting the Twins: It is way more important to phase Karam Magespear sooner then to deal with a hand. If you know you can survive a blast then interupt the next one from the hand and Karam is close to 33%, focus Karam to phase him then finish off that hand. The hands will always spawn behind Karam, getting a good position on him can be key to spawning hands in a nice spot. Hands will despawn after killing Karam so if he is close to dead kill him off and the hands will despawn. Pets can soak the runes, very helpful if the runes spawn on all the little adds, I also think runes will spawn close to where the first one spawned. Learning how to kite effectively is key here, when you are dealing with him and hands use stuns/slow on karam to deal with hands. Little adds don't really need to be killed at all as they are very slow and in fact in some cases help you with resources such as mage and druid.An Impossible Foe: The imps that explode that leave fire on the ground don't have to be killed if you can get them off to the side and let them explode there, allows for more up time on Agatha. If you have a Draught of Souls it can be very helpful to save it for the absorb shields. For unholy death knight I found that the Shadow Infusion talent was very helpful in handling adds and getting through shields.End of the Risen Threat: Good luck with this one, really nails the whole "Needing patience to be a healer" aspect. Learn you use your CC effectively for that first phase and don't release on the final phase your allies can still kill him giving you credit. The third phase is the hardest part of the whole encounter and it takes a while to get to that point. Take all the time you need to prepare for that going in and good luck.The Highlord's Return: Orbs can be used to reset stacks, so you can get a bunch of stacks and hit an orb which allows more dps uptime on Variss. Eyes will despawn going into phase 2. Be on the move constantly in phase two, don't double take at all.As I said before if you have any specific question feel free to ask. My characters on the armory are still mostly wearing the gear they had when they did the challenge besides my rogue and paladin. I love these encounters they are so much fun and add another layer to the game, I really hope blizzard does more of this sort of stuff in the future.