I find judging the level of "classes" to be an almost entirely useless enterprise. Specific builds, yes, classes, no. I am sure I can make a crappy Druid, provided I pick the wrong spells, feats, etc.
Is it perhaps difficult to make a Rogue or a Soulknife that can hang w/ a party of well-built psions, psywarriors, wizards, Zhentarim skymages, and what have you? Sure, but it can and has been done. I've played whole campaigns (3rd to 15th level, a fair range for assessment, right?) where this was the case. That, I contend, is kind of the point of Charopp.
EDIT: I should qualify the above w/ relevant to the challenges and adventuring things that interesting in a D&D game. I'm sure wizards can modify the world more than a rogue can (although maybe not ... query what robbing the entire nation's gold supply would do).