As the title suggests, I believe positionals are a inherently bad design. Even putting aside the lack of clear feedback for successful hits, this mechanic is problematic in a way that cannot be fixed.
Bosses can't turn frequently, and if they do, they have to do so in a predictable manner, or melee dps can't hit positionals consistently. There's a cap of how much a boss can move around (or force players to move around) before melee dps run out of true north uptime.
Unique positioning requirements (like facing a boss toward a stacked party for a extended period of time) are avoided because melee dps can't hit positionals.
In overland or solo instances, hitting positionals is inconsistent at best since enemies tries to face toward you most of the time.
How the game currently handle the abovementioned problems are to either limit boss movement, which doesn't have to be the case if there are no positionals, or make enemies ignore positionals, which renders it pointless anyway.