It really depends on what you mean by "casual." You would be right if you define "casual" as simply not doing end-game. I might classify "casual" more as not putting nearly as many hours/week into the game, and not on a schedule.
you need to listen more carefully.
Spoiler: show
people wont skill on feather tickle birds. i can see people spamming sea though and such areas like lufaise/krt/beatsmen strongholds. I personally plan to skill up in sea.
Why does feather tickle matter? You just need to swing your weapon and hit.
What's stopping you from going to birds as a duo (or solo + dbox) and fighting them for skillups? They'll be EM-T, ripe for skill.
While there are better places to skillup, I am pretty sure peoples inner laziness will drive them to birds or MMJSP for skillups. Honestly I think the Wamouracampa would be good skill since they take a beating well when they curl up but outside ToAU would prolly be better to skillup.
A zone in the past would be nice. Sigil eva and PDT bonuses on EM and lower, plus regen/refresh/etc. The only thing that really comes to mind in terms of lvl 80ish monsters is beastmen strongholds, though. Or Northlands.
I really think they will adjust some mob lvls/mob types in alot of "underused" zones.
Probably anything that is currently underused, or not used at all and doesnt affect low lvl gameplay, like lets say Kuftal Tunnel behind the rock (tigers, cockatrice, wyverns), can most likely get adjusted, I mean who goes to exp there in kuftal tunnel anymore? Not even BSTs use this as a camp to fight mobs.
Uleguerand comes to mind!
Basicly everything where FoV didnt have a big impact on, or where pts/soloers/BST dont go/no NM spawns, there are alot spots open for this.
Zones I see with a practical mob type/increase in lvl:
Uleguerand Range
Kuftal Tunnel (behind the rock part)
Small fields left out on capped CoP areas, that are not required to walk through for missions. (could still allways add more floating lsland to riverne)
Revamp of mobs in Lufaise Meadows (probably not because of Aegis Sheep NM)
King Ranperre Tomb (most likely not because of Vrtra)
Ro'maeve Moon gate (very likely)
Halvung
Caedarva Mire
Just some, but its very delicate, with some of the old NMs that spawn there, so it will most likely just be a small-medium spot far fetched away where higher lvl mobs will be or so
Moblin Maze Mongers anyone?