yeah, that's a pretty much spot on description.
I also find it interesting, that Charlie is pretty much the only character that has remained prtty much the same as when the show started, more or less. Dee as well in some regard.
Mac, Dennis, and Frank have evolved quite a bit.
Dennis and Frank especially - though, it totally opposite directions.
I'd say in order of evolution, started with who evolved the most
Dennis
Frank
Mac
Dee
Charlie
so much so that now, Charlie is 'sort of' the most normal of the group
.
dumb as a bag of hammers, but "normal" in the IASIP world.