Both Northreach and Dryfoot feel like they have plenty of intuitive quest lines that encourage the player to engage with content throughout the zone. These are quests that can be started solo but often lead you to places where you'll need to engage with other players to successfully complete the content. They also put you in places where named mobs often spawn which can potentially lure a player back to engage with the content again.
Meadowlands has a good portion of this as well. There's quests to justify engaging with exiles, wolves/spiders and even crocs if you count Tradeswoman's Lament (despite the abysmal quest reward). There might be a benefit to implementing a introductory quests that encourage players to kill 3 chevron aggressive bunnies (during daytime) and 3 chevron emberflies (during night time.). Give players an organic reason to hunt big bugs or big bunnies so they have an opportunity to run into Quillbane, Hobfly, Zofly, or any of the countless named noobs barely know exist. These mobs drop amazing loot and they're underutilized carrots on a stick screaming to be properly wielded.
Redshore's Shoring Up Redshore questline feels like it was developed with the assumption that players would be starting the zone from the Dryfoot side. After the DF camp it sends you through snatchscale pass (yikes) to the beach exile camps, then the lumbermill, then the ruins. That's all fine and dandy, but you're actively sending people new to Redshore to their death in Snatchscale Pass. Since the monolith was moved to the west side, and players are more organically starting Redshore on the west side. Perhaps it's worth considering moving the quest giver to the Fort?
If we split Redshore into quadrants The Stranger quest checks off the box at the bottom right (southeast) side of the map. That leaves the northeast corner, the northwest corner, and even the southwest corners as largely barren of quests that will lead players to areas that are otherwise left unexplored. Since named in Redshore spawn in spots throughout these corners of the map they might as well not exist for players that actively seeking them out. Potentially they might find them by gathering but even then most people are incentivized to gather in the more hospitible zones (Grimstone Canyon at 30 or Highland Hills at 20).
The lower part of Highland Hills could use substantially more quests but personally I wish it didn't exist to begin with. Level 20-25 content is already fragmented throughout the world geographically between Dryfoot and Meadowlands Spiders and UC. I personally wish HH was 40+ entirely, but now I'm getting off topic.
GC feels pretty good coverage wise. That is likely because of how narrow the space is, so it makes it a bit easier to blanket cover each region with an appropriate quest. I would love to see more Cliffwalker pieces of gear in that level range though that could be more easily done by rewarding multiple gear pieces throughout the stages of the existing quest line.
Perhaps the fort outside GC in DF where Wrax spawns could use some attention on the quest front. It's a very scenic camp with little to incentivize players to engage with it outside of a half-decent stamina shirt or a necklace with avoid on it.
Overall, I think quests are in a pretty good place. Outside of Redshore, I feel most zones are pretty well fleshed out in respect to quests. That said, I think there are some obvious ways that existing quest lines could be improved and made to feel more rewarding. Then again I don't really expect structural changes to existing questlines to happen as those that have completed said questline might be upset that they can't redo them. Maybe those types of major changes could happen during our first Season/TLE/Relaunch if that pie in the sky idea ever comes to fruition?
Zig