Question, why does Bard and Machinist share the same core mechanic?

[Airget]

Does anybody know if there is logic behind this? I feel like both lose their uniqueness due to their similarities in skills and how they are played.

Because the ability for ranged to move around freely without restriction and still deal damage was imbalanced. It was easier for Archer/Bard to pretty much ignore mechanics and continue fighting, meanwhile both Blackmage/Summoner and Melee have to do their dance and avoid doing DPS during certain parts. That's why Machinist/Bards get the charge abilities they get to balance it so that they need to be more mindful with enemy AOE effects rather than just run around like chickens with their heads cut off.