I get the feeling that Rocksmith is extremely persnickety about chords, even in standard tuning. You have to hit all of the strings in the chord at exactly the right time with exactly the right balance between all of the notes (well, there's a bit of leeway probably but it seems kind of random), otherwise you'll get a 'miss'. It's too bad Rocksmith can't tell us why it gives a miss. It's because polyphonic pitch detection is extremely hard. Nobody has perfected it at a level of a trained ear yet, nobody. If you can do it reasonably well you'll end up with a number of technical grammys (see: melodyne)