Basically you're right: what do the options mean? Especially non-experienced administrators can cause quite a mess in setting them wrongly.

But having had lengthy discussions and various ideas how to shorten overlong forms in drupal, I see this with a laughing and a crying eye. The permission form is already one of the longest. With descriptions, it will span from Vancouver to Denver and back...

Solution idea 1: strongly think about the "help text toggle" option http://demo.guruburu.com/ that experienced administrators will use with joy to get the list back to the old size at least.

Sulution idea 2: (much favored): Keep the help texts (and maybe also help text toggle), but as well as for Modules page, think about a way to break it up. Maybe by use of two columns (like this mockup for translation server illustrates, even if it cannot be directly compared http://drupal.org/node/215286 ), by use of pagination, or how about grouping things more tigthly in some way like the Views UI Mockup does to tame the beast Views edit page http://www.couzinhub.com/Views2-UI/views2-9.pdf )

Rather than scratching we should think of healing the wound ;)
I'll stand to my word and be handy at least with mockups.