Want to know why tank is almost always the role in need?

[Jojoya]

Probably a stupid question but bard have an ability to speed up the whole party (sorry name escapes me atm). Is that effective enough to be used instead of sprint for this sort of mitigation?

ie If you have a bard and they are using their ability liberally can a tank then save sprint for other things?

These are genuine questions not trolls.

Peloton (available to all the Phys ranged jobs) only applies when out of combat. The moment the player is on a creature's enmity list (as opposed to being hit by them), the effect is removed.

It's helpful getting to the next group of mobs faster after a boss dies but doesn't offer any advantage when it comes to mitigation.