Hide and Move silently at 20 is actually better than invis since they sometimes spot the invisible.
As for the mushroom groove it was levelup haven for lowlevel solo archers, firebursting wizards (buy scrolls) and whatnot before the mushroom guys (and areas
But even they are easy meat as long as you can reach ac 25-27 or whoop them quickly (fireburst usually do the trick).
My lv5 wizard would cashgrind there right now if it wasnt for the low xp and her limited carrying ability.
Back in the day we would do varalla's passage, then mushroom groove for lv2, lv3 at slaves and on to west of varallas. Most fighters can solo west of varallas at lv3.
Fire river was/is considered too hard alone, then again why be alone?
Now we have the sewers and tombs as well.
I believe it is called development and we love the builders for it.