I'll have to strongly disagree with you on Tarzan. It's been Disney's biggest animated hit since Lion King making close to $450 million worldwide in 1999 dollars with $171 million in the domestic market. Not adjusting for inflation, it's still higher than Lilo and Stitch, Princess and the Frog and Brother Bear, Disney's top worldwide grossing 2-D animated films of the last decade. If we were to adjust for inflation (to 2009 average ticket price) the original total of $448 million would become $645 million.
If there's a reason it hasn't been recently exploited it's likely the extra cost in producing anything related to the character. Ever notice the special extra credit to the original author every time Disney uses him (see Kingdom Hearts as an example)?
As I understand it the character's likeness isn't exclusively owned by Disney like the Pixar creations, Pirates or even unoriginal characters based on public domain stories, which probably results in higher costs in making anything related to the movie. Merchandise may not have sold as well as the Pixar/Pirates stuff either which could explain why Disney has shoved the film aside despite its legitimate box office and critical success.
I do however agree with your latest defense point.