once again, with the example you stated, you're assuming someone with exceptional stats, years of dedication, and an even more zealous pursuit (skill focus) than most. she will have other skills that need attention too. also, do you roll stats for everyone in the town/world? no, you probalby don't. for the most part everyone else is just Joe Schmoe. a few will have better than average abilities but only a few.
PC are supposed to be exceptional people. of course, they're not the only exceptional ones in the world, and their antithesis may actuay exist. but those should be memorable occasions.
as for the extra planar attention, set a value, and use percentiles to see,
IF a performance catches any attention, and then again to see
IF the being actually does anything. the same being seeing/hearing the same mortal over and over giving amazing performances might want to pop in to say hi.
by the same token, if a PC bard gives an amazing performance, and it catches someone's attention, they may decide to keep an ear/eye out for them, and when the next performance is lackluster they quickly lose interest in the mortal who just got lucky.
also, i could be wrong, but aren't those rules for attracting extraplanar creatures used for when the bard is specifically performing for a crowd? somehow i always thought that using the perform skill to, inspire courage or countersong for example, didn't really count as the same thing. just coz you're using hte same skill doesn't mean that you use it the same way. right? or have i lost my mind again and haven't realised? "p
there's always a way to work these things out. but it's important to note than in all that i've said, i've never DMed before, so make sure you take it with a grain or two of salt
~NegZ