The fact that Artifact Power rewards from quests and treasures now scale with Knowledge is not a bug.
We started off the design of the system thinking along the exact same lines as many of the posters in this thread: We figured that we should make sure that one-time AP rewards did not scale, or else the "right" answer might be to delay completing key quests or collecting any treasures until you had higher Knowledge. And that didn't sound like much fun.
So we spent the first half of beta with all repeatable AP sources (world quests, item drops, missions, etc.) scaling, and all story quests and treasures flat. We added multipliers to things like Suramar or Order Campaign quests that tried to incorporate a likely expected Knowledge level at the point where players would get to that content. So, for example, finishing the third chapter of the Suramar campaign awarded a flat 10k Artifact Power, since by that point we expected players to likely have a ~14x multiplier from being around Knowledge Level 12, and we wanted to make sure that the reward still felt meaningful to that player.
But as we were actually playtesting extensively and getting into endgame ourselves and going through the Artifact Power and Knowledge progressions, we realized two things:
- Artifact Power isn't a limited resource. There's always more available. There are world quests popping up every few hours, dungeons that can be repeatedly run, and so forth. And regardless of what we did with one-time sources, the vast majority of a player's AP over the course of the expansion would come from repeatable sources.
- Even trying to account for an expected "par" Knowledge level, any time you came across a non-scaling reward that was aimed at someone with a lower Knowledge level, it felt pretty bad. Stumbling across a zone side-quest you'd missed and getting 100 AP from it when you needed 70k for your next trait felt like a waste of time. Opening a treasure to get 25 AP when you needed 300k for your next trait felt insulting. The system we'd set up actually encouraged trying to front-load all your AP while it still mattered (e.g. doing a full world tour to collect every treasure possible while still at Knowledge Level 1, since if you waited they'd no longer be worth the time relative to other activities).
So we started changing it. The first step was making treasures and level-up quests scale. That helped, but we still found that someone who delayed doing much in Suramar beyond the initial Friendly unlock, and instead focused on other content (dungeons, world quests, etc.), found all the rewards in the zone incredibly underwhelming once they got around to doing those quests. So just over a month ago, we also converted those rewards to be scaling sources.
Now, we haven't had a new client build since then, so community sites and datamining likely still show the values of the old items. That Suramar Chapter 3 capstone reward mentioned above is not a 10k AP item that gets multiplied by Artifact Power - that'd be pretty crazy. It's now just a 750 AP base item, which will give around 10k AP when you get there if you've been keeping up with your Knowledge.
It's not necessarily intuitive, since at first glance it seems like an obvious flaw in our system that if you wait until Knowledge Level 20 (a month and a half longer) to complete that quest, it'd give over 70k AP instead of 10k. Aren't you "wasting" 60k AP if you don't do that? The key here is that everything is relative. That Suramar quest capstone reward is equal to ~5 world quests. It'll be equal to 5 world quests if you do it ASAP; it'll be equal to 5 world quests if you do it two months later. And it'll contribute roughly the same amount towards whatever trait you're working on at the time.
Finally, it's also worth noting that the biggest one-time sources of AP are the Order Hall campaign, and the Suramar campaign. From a pure min-max perspective (probably the mindset most associated with the competitive raider), you really don't want to delay turning in either of those. The former leads to unlocking your third Artifact relic slot; the latter unlocks additional repeatable sources of AP (new world quests) and eventually access to the two Mythic dungeons, for an extra two Mythic clears each week.
tl;dr: Just get Artifact Power when you find it, as you find it. Enjoy the rewards and the immediate benefit, and you aren't hurting yourself in the long run