A Bards point of view.

[Tupsi]

snip

1. I rarely see people say to never use a song, that's actually the first time I've heard that may even be a thing. (Probably a stigma from other generic MMOs.)
2. This doesn't happen with Foe Req, but the other songs doesn't drop your DPS so significantly that you shouldn't use them when needed, you're not the only DPS there most likely.
3. When you have casters, especially a couple of blm (or more if its alliance content), I'm pretty sure asking for Foe when you're not using is indeed knowing when it's best. Other utility songs is up to the situation, but a lot of times BRDs don't even use em at all..which is largely the point of that other thread.
4. I've rarely seen this..in T4 pre echo I see TP being requested a lot though.
5. Indeed - This is why BRDs carry potions to replenish their draining MP to extend song duration when need be, or rotate songs if there's 2 BRDs in party.