I know that many things are still in the development stage and not all of what we've currently seen is indicative of what live will be like, but I believe that adding a buff timer for straight shot to Bards song UI will go a long way in quality of life improvements. While 4.0 will add many new mechanics that go a long way in being able to optimally control buffs/debuffs required by the class (30 sec dots, ironjaws is instant, etc), square has certainly increased the level of things that Bards now have to monitor in multiple UI locations.
For many classes (DRG, Monk, BLM) their rotations are typically designed in such a way, because of combos/timers, to create very cyclic like rotations that when correctly played will passively refresh buffs and dots that need to be maintained for the class. For example HT IDC44 TTT44 rotation will automatically refresh HT and CT dots when their time is required by simply executing the rotation. This allows DRG to only need to focus on eye stacks and ability cd timers (correctly done DRG wont have to really worry about BotD timers now that FnC and WT can be used back to back for 20 sec additions). As Bard/MCH have no real rotation and with the introduction of refulgent arrow, we will have a more difficult time maintaining our crit buff with overall maintenance mechanics. Bard in 4.0 will have to monitor straight shot buff as it will not likely be refreshed often with straighter shot procs now that refulgent arrow can consume these, Dot timers, Song timers, song stack mechanics, basic CD timers MP, and ability procs.
While the maintenance of all of these mechanics will add a great deal of depth to the class, the fact that all of these things will be in various UI locations will have our eyes jumping all over the screen and not paying attention to the fight. Some classes have been designed in such a way that outside of cd timers, they have nothing to monitor outside of their new class UI; especially classes that have no real procs, out of combo dots, and cyclic combo rotations. I think the current design of Bard will be incredibly fun and rewarding to play, although, I think that doing something as simple as adding our maintenance crit buff to the song UI and giving us one less place to have to focus our attention throughout a fight will go a long way in promoting the fluidity of the class.