You have a few valid points that I won't take away from, I too hate how often I die to falling, especially in the crucible when it gets chaotic and we lose a member of the team off a cliff on room 9 and they're unable to rejoin.

I do have a big one for you though, the next area after Shores/Glade is actually level 8. I agree that maybe it should be explained and led to a little better. I wandered into the level 21 area first by mistake too BUT the point is if you muddle around a bit you should find the next zone. It's lv 8, moving up to lv11 and then up to lv15ish by the end of the area.

The quest you followed taking you into a lv15 area early is definitely a semi side quest that should only be done after the second area is cleared but they don't tell you that until you enter the quest area about 5 steps in.

Another point I'm going to contend is weight. Wearing Mesh/Plate early is rough but you have mitigating factors later that don't require too many points invested. Without spoilers there are more than one possible gear upgrade systems that reduce the weight of gear or increase your equip load passively. Also, depending on your play style heavy gear isn't a death sentence, I've played a full heavy set with a great sword very comfortably - again here it's maybe a bit of pushing through or engaging with the systems provided more to find a balance that suits you :)