I'm not sure "quantity" is necessary; maybe. I saw Gene Simmons solo in a 1,000 seat club, and while it was mostly Gene's solo songs and songs he wrote while in Kiss, it was more about the fact that he was presenting himself in that setting. No bombs, no fire, no blood, no breathing fire, no Paul, nothing but the nakedness of him singing those songs with three other guys.
Same with when I saw Billy Squier with GE Smith; I'm a huge Squier fan, and I'm not sure there was more than one or two songs in that set that I would have picked had I done the setlist ("in The Dark" and "Too Daze Gone"). Yet it was magical, because they were songs that HE picked to tell the story.
What's the difference between giving us The Astonishing and "Don't Look Past Me"? Do you think all 2,500 people at every show were clamoring with passion for each song of that cycle? They had their reasons and we accepted it. Same with obscure songs, in my opinion.