as i said, i have the same setup as OP. i DO subscribe to local channels. in charlottesville, ABC, Fox, and CBS started broadcasting OTA digitally in january. these are the channels with no EPG data. NBC and PBS have been OTA for years, and these are the channels WITH EPG data.
what i'm trying to determine is when, how, and if Dish will provide EPG for the new digital OTA channels. i've called them a few times and they act like i'm speaking a foreign language.
if i use your "20%" heuristic, we should only have problems with 1 of the 5 channels, not 3 of 5. if you have any other insights other than "don't expect yours," that would be helpful.