I agree, casting times should be removed.
That's not a matter of efficiency, bard can have a decent dps and are pretty useful still, but a matter of playstyle.
What if they added a stance to summoner that increase their dps by 30% but remove their pet? Effectively turning them into Dots blackmage. What if they added another stance to bard that increase damage by 20% when in melee range of a mob? Effectively turning them into melee dps.

All those change would not impact the effectiveness of those class, but it does change the playstyle massively, playstyle is important, that's why we people play Ninja instead of Monk or vice versa, that's why we don't have simply 1 job for each role.

Variety, create fun, and allows people to find a job with a playstyle, with a rotation and look and feel they enjoy. Wanderer's Minuet has altered the bard playstyle and as such is big mistake.

Every people saying "The bard are fine" are focused on effectiveness.