I have looked at both the English and Japanese sides of this forum, and found it worrying that dev implemented button mergers to DRG and BRD that are almost unanimously hated. I understand that I do not represent everyone, so I started this thread as a place for everyone to discuss what buttons should or should not be merged.
CHANGES THAT ARE HATED
Dragoon
In 6.1, "High Jump" was merged with "Mirage Dive". This received immediate outcry that dev decided to add a small delay after "Jump/High Jump".
What was the problem?
"Mirage Dive" is an ability that follows the ability "High Jump", and needs to be carefully executed either before or after "Geirskogul" due to Dragoon's job design. Becoming the same button causes unwanted use of "Mirage Dive" right after "High Jump" when players "queue" abilities.
The small delay added in 6.11 needs to be tested out, but that seems to be fixing something in a weird way that was never broken, until they broke it deliberately.
Bard
In 6.1, "Pitch Perfect" was merged with "The Wanderer's Minuet". It caused a glitch that there can be a situation where one of the two actions can't be used when there are two bards in the same party, and has been fixed in 6.11.
What was the problem?
The problem wasn't only the glitch. "The Wanderer's Minuet" is an ability that is used every 2 minutes as part of the job's rotation, while "Pitch Perfect" is an ability that is used about every 9 seconds within a 42-second timeframe.
Due to the difference in usage, a lot of players put these two buttons at very different parts of the hotbars, where "Pitch Perfect" is usually at a place easily accessible. Merging the two buttons caused unwanted execution of "The Wanderer's Minuet" in some players.
Besides, Dragoon and Bard never had a problem with hotbar spaces, so there were a lot of question marks after the sudden change. These two mergers should be reverted as soon as possible.
CHANGES THAT ARE POSSIBLE
These are just some actions off the top of my head and is by no means exhaustive.
Samurai
Samurai faces a button bloat problem, where a large number of the abilities have single/AoE counterparts sharing a recast timer. The single attacks can be upgraded to the AoE versions with fall-off as they level up.
Dancer
"Starfall Dance" and "Fan Dance IV" can be merged with the buttons that allow their uses ("Devilment" and "Flourish" respectively). It wouldn't cause the same problem as Dragoon because they are usually executed right after proc during the burst window.
Summoner
You may think Summoner already has the fewest buttons in the whole game. But "Ruin IV" can be merged with "Energy Drain/Energy Siphon" due to a similar reason as Dancer, although "Ruin IV" is usually saved for movement. I understand some players want "Astral Flow" to be separated into different buttons and that's where a button can be removed.