Anything tier 3 or above rapes it just as well.
To be fair, WLD is premised on 10-20 encounters/day with few chances for rest, and lots of interrupted/hostile/dangerous resting. That is problematic for some of the Tier 1's, some of the time, especially in the lower level areas.
It makes a lot of stupid assumptions, like the fact that it's impossible to wedge a door shut for some inexplicable reason, or that you can't use druids or wizards effectively.
And all those encounters screw BSFs more than anyone, so you need infinite healing from an early level just to survive.
...assuming you're too dumb to live and can't figure out how to hole yourself up in an empty room.