Really? Please tell me a realistic scenario where you can plan things like that. Not even in T4 you can plan things ahead. Yes, I know it's obvious that during pack of mobs, DPS are expected to use AoE skills, but still you'll never know when they're about to dry until the DPS calls it out. Hence, you respond by providing what the DPS needs.
Your example was too biased, obviously with that kind of lineup, it's a no-brainer that the Bard should use TP song, if you actually look at my previous post, using TP song depends on the party lineup.