Thanalan's = Reachable, blocked by drakes, eyes and gnats but they have space to move.
Gridania's = Next to impossible due to narrow passages...and boars + drakes.
LL's unknown.
Any chance Grid's can be opened up a little? Perhaps have at least 1 path that a lvl 50 can possibly have a chance of running through?
Sight-only mobs instead of sound ones...3 x Raptors is doable...3 x drakes in the same area is not.
Path to Alder Springs can be used as an example. Sound mobs in clearings and sight mobs in narrow passages.
Edit: Snakemolt, Ruins north of Moss and the ones north and south of Crimson Bark are quite impossible to reach. The rest are ok.
If anyone is asking why...its for the achievements before the cataclysm called 2.0.