I've met some very interesting bards in my time who don't even dot in expert roulettes so I've ended up giving my partner to tanks before after the first boss. It's also likely better in cases where they keep floor tanking which i see in dungeons.
I don't know if i have really cursed dancer runs but I almost always end up with a DPS I can barely trust to give my partner to, though usually if im doing duties I don't always pay attention to others.
Though in your case a fully melded dancer would pretty much always be better then a tank.
