I was actually building up some maps for artifacts (mostly for the new Twisted sets, which require Omen Sight), but they didn't quite make it up to snuff for an article. If you'd like me to post some of my maps anyway, I could do so.
Keep in mind you probably won't be able to afford Omen Sight until at least level 40; it costs 25,000 planarite.
In general, I've found good artifacts are really rare. A few patches ago they bumped up the chance of a rare find, but they also extremely decreased the respawn rate. I'd estimate the chance of a green at 10% and a blue at 5% from any spawn. Best bet is to keep looking. There are some spots that will always be either a green or a blue. For example, in Gloamwood there is a cave with roots near the instance (lots of spiders and goblins). On the roots there are spawns that will always be at least a green in rarity. But they involve a bunch of tricky jumps.
Some decent spots off the top of my head:
Freemarch: The Rill Pond. There are several spawn points here and I've found a couple of blues. Also, the Iron Fortress has a lot of spawns, but a lot of enemies as well.
Silverwood: The northern mountain range. Start northeast of the instance and just follow along the top of the mountains. Have found several blues here. Another great spot is the puzzle for the zone; usually around 3-5 spawns on top of the towers (look all around). Lots of greens and a couple blues from there.
Gloamwood: Besides what was mentioned above, I found a lot of blues in Shadefallen Keep. Look especially in the towers (some require jumping skills). An amazing location is on top of a tent on the highest level. You need to jump off some ramparts to get to it, but I've found 4 blues in that one spot. Finally, the mountains south and southeast of Gloamwood Pines have a lot of artifact spawns at the base of the small trees.
Stonefield: Honestly they are all over. I always find a lot of spawns outside of Deepstrike Mines. Look in mine carts and on scaffolding.
Those are all the zones I've mostly finished. Still trying other zones, but the Twisted sets hold my attention for now