You used to get them from salvaging legendaries but this is no longer the case. Now you seemingly have to farm world bosses? It’s wild that I’m level 100 and still can’t afford to add slots to my gear since I have a sum total of three.
Also still pissed off that they removed attack speed from weapons entirely without even letting us know in the patch notes…???
errrr, i dont think you got them from salvaging to be honest, tho im not 100% sure, what i know tho is that goblins used to drop them, along with world bosses. Also id say im pretty sure world bosses dropped more than just 1. which does feel a little odd indeed as you are locked to 1 socket per 3 hours.
WB’s seem to be the sure bet. Yes they are less frequent.
Just killed the WB for the first time this season (WT2) and didn’t get any prisms. Wasn’t it supposed to be guaranteed drop from the WB?
WB and treasure goblins will drop them
I seem to get 1 from every WB in WT4 I still need more sockets in my ancestral gear I just switched to.
In S3 I would also get them from doing the events inside the NMD’s. I’m not that far into the game yet to tell in S4.
Yup just did 1 world boss, and got exactly 1 Prism…Still have like 5 holes to drill this will take a while. But at least my 925 Unique is done that one won’t change.
They were occasionally dropping in legion events but I’m not getting loot from legion chests. I’m getting one piece of gear at best.
I’ve done a single WB and have a single prism. Nothing else seems to drop them. Very inconvenient because I tend to miss WBs because of a combination of not paying attention and just not playing at the right times.
It drops from Legion too but the amount is lower and sometimes not drop at all.
Globin used to guaranteed drop prism but now is either stop dropping or the drop rate is too low to observe it happens.
I don’t see how I would ever try more than 1 or 2 builds a season if the prism a d gold drops are going to be this ridiculously low.
I had 2, but I hadn’t done any world bosses. I had done a couple of Legion events though, and since people suggested it here, I tried another Legion event, and I did indeed get another prism from that.
As a HC player, I’m glad there is still an alternative source outside of World Bosses, since I won’t do those often in HC… but I do wish they were a bit more widely available, since they are very helpful for survival.
At least it’ll give me a reason do do more Legion events, because those were useless to me before, so I never bothered. I’ll try doing those whenever I can, and see if it nets me enough to scrape by… 
This is my main beef with this season. Prizms for adding sockets. They are only dropping from World Bosses and so I have gotten 4.
I’m level 82.
Totally unacceptable as it makes new, better pieces of gear unusable if one is relying on sockets for resistances etc
It makes them too rare and gated behind timed events that are not frequent enough. Bad Blizzard
It does seem like they’re dropping from Legion events, as people have helpfully reported above. 
I share your frustration, because it definitely feels like the supply is far too limited, considering how often we upgrade our gear. I think it’s fine if we have to be a bit more selective about when we use them, but it would be nice to have enough to even be able to use them at all.
I did at least 10 legions yesterday, not a single prism. Are you basing this on last season?
Yea, I remember how hard these were to come by, which is why I’m playing eternal this season, since the new goodies aren’t gated behind the “start from scratch” thing this season 
.
Some people suggested above that it’s not a guaranteed drop, who knows what the conditions and percentages are? I did three today so far on WT3. Here’s my results:
I soloed the first two Legion events and each time I got 1x Scattered Prism, even though I didn’t get the mastery (only got 2 chests).
The one I just did now, we had a group of like 5-6 people, I didn’t get a Scattered Prism drop (even though we did get the mastery).
This is all probably irrelevant and it’s probably just a random % drop, but since that’s the only information I have for you, there it is.
As I said, this season I’m not getting any loot from WT2 legions. Just a couple pieces of gear across all three chests. They’re bugged.
Last season I got an occasional scattered prism from legions.
You’ve never gotten these from salvaging. They were drops from world bosses (usually) and legion events, and very rarely elites. But currently they’re almost nonexistent and they are not even dropping from world bosses for the most part anymore.
Legion chests are bugged. Massively. Getting 1-2 items, usually a blue and yellow, and no obols makes these worthless events until it’s fixed. Somehow the devs broke a ton of stuff and once again, between the PTR and live no less, which means they should have had a second PTR since they obviously made significant changes that borked a lot of systems.