Blizzard courted some controversy a few weeks ago when it became apparent that those on the "Balance of Power" quest chain could not obtain the quest items required for it within the LFR difficulty of Emerald Nightmare, instead requiring Normal or higher difficulties, despite there being no indication of this in the quest text.
Frankly, I was expecting this to be the case, as earlier steps in the chain required players to run two dungeons on Mythic difficulty, which would mean that the raiding portion would be a step down in difficulty if LFR was an acceptable method of acquisition.
Still, in the absence of a Mists or Warlords style legendary chain, this seemed like the next variation - not an expansion-spanning legendary chain, but at least something to keep people running LFR.
At this point, my main character has an average item level of 850, thanks to lucky gear upgrades and Mythic dungeon loot. The Emerald Nightmare raid on LFR provides 835 gear. I do enjoy the raid (actually, I'm very fond of it) but I find that I'm basically running it purely for the acquisition of transmog gear. This might change with Trial of Valor (the quality of whose rewards I do not yet know) and Nighthold (which, at 845, could provide some upgrades and would of course be more likely to Warforge or Titanforge up to an attractive level.
But while Blizzard tries to figure out exactly how to make the various kinds of content rewarding (in fact, if you completely stay away from manually-made PUGs, LFR should provide you with some attractive gear,) the issue, I think, that is bigger is a cosmetic one.
The reward for the Balance of Power chain (which begins with Kalecgos appearing in your class hall) is a cosmetic one - a new model for your artifact weapon. Blizzard has, reasonably I think, argued that people should not get so upset about missing out on these quests given that the reward is entirely cosmetic. Still, that raises another issue, one that we have been thinking about since the introduction of the artifact weapon concept.
Everyone's weapons look alike.
Now, to be fair, it's not as bad as it might be - a Destruction Warlock and an Affliction Warlock have totally different looking staves. And if you look at the era of, say, when Highmaul was the only raid available at the start of Warlords (very analogous to our current situation in Legion,) there were only I think two staff models that you'd see Priests, Mages, Warlocks, Druids, Monks, and Shamans using.
And of course, one is free to transmog over one's artifact weapons. Personally, I don't do that because, well, if I'm going to be wielding an artifact of incredible power, I feel that it ought to look like itself, even if it is a rather radical variation thereof.
I finally got my first secret artifact appearance - doable easily because it did not require me to farm for rare drops (actually, the official method does require one to do so, and in fact I found the item I needed, but I made my first attempt without it.) This was the Havoc Demon Hunter secret appearance, which transforms the Twinblades of the Deceiver into glaives that appear to be made of demon bones and teeth.
Incidentally, to get this you'll want to either glide down from the peak of Highmountain toward Felsoul Hold or farm the demons there for Candrael's charm. The latter can be brought to a female demon hunter on a hill on the west side of the hold (you'll want to climb up out of the pit back to where it's grassy) and if you give it to her, she will launch you toward the target, a massive Felbat named Downfall. Downfall will create a patch of wind around him that allows you to fly, but periodically he'll punt you away and you'll want to use Glide to make sure you get back into his air pocket. I found that, being hesitant to use Fel Rush in a small space, it was easier to complete this in Vengeance spec. Downfall simply drops the item needed to grant the special appearance for the Twinblades, which can be collected in either spec but can only be activated when you're in the proper one.
Demon Hunters demonstrate the need for more artifact appearances I think better than anyone else, as Warglaives are a brand-new type of weapon, and if you want to keep that classic demon hunter look, you're very limited in your options.
The good news is that Legion has only been out a little over a month, and Blizzard claims that the expansion is slated to have a lot of content patches. 7.1 is currently on the PTR, though I haven't heard about any other artifact appearances. There was another set datamined from the Beta, though they have not shown up in game.
I'm hoping that we'll get many more of these over time - as impressive as it was to see Truthguard upgraded from its original form to its Heroic variant at the end of the class campaign, I wouldn't mind seeing another version of it. And while I keep doing the Withered Army Training, so far I have not had any luck with the hidden appearance item.