I guess from a balance perspective 5* abilities are not meant to be things you run around with higher hones. When I get enough orbs to make full break R3 I'm not sure if I will as so far if I need more than R2 I actually need a better strategy/relics.
Some points on that discussion are really sound.
Really though, it's fundamentally a question of straight-out damage vs utility. About half a year ago, everyone was running r2 Breakdowns because 4 shots was 'enough' to get through bosses. You technically don't need more than a r2 Buster for whatever stat debuff gimmick a fight has. For those skills, more hones generally are just to do more damage. This holds true through things like Full Break (you get more uses, which translates into more damage firstly and a longer battle secondly) and Meteor (generally this would be for clearing trash, but more hones are good for more sustained DPS on a boss).
On straight-out damage abilities, though, more hones translates directly into more damage (yes, that sentence sounds stupid lol)
Compared a r4 -ja nuke, which caps out at 80000 damage done total, Barrage/Exploding Fist/Thief Raid only needs to do 20k damage a pop (which isn't hard with buff-stacking meta like Planet Protector, etc) to do equivalent total damage at r2, and accomplishes this in less turns.
This really mirrors the jump from 3* to 4* abilities. Utilities gained in their actual utility while doing little additional damage, and (magic) damage abilities jumped almost double. The best practice was to hone utilities to r2, and damage abilities (Waterja!) to r4. I think that holds true going from 4* to 5*. I'm keeping Full Break at r2 for foreseeable future because 12 turns is still more than enough to cover any boss fight, or any burn phase of a boss fight. Damage abilities, on the other hand, are going to be r4 first. Bahamut is a likely candidate depending how soon we get summon balance changes. I'm probably going to bite the bullet on Barrage just because it can be used by far more people than Thief Raid/Exploding Fist and the 'higher-tier' replacement for it is more than a couple of months off. And we're gonna be neck deep in BSB meta anyway.
edit: Should also say, the above holds true while 4* abilities are still 9999-cap-limited. When bosses start having absurd DEF/RES, then the total difference between 4* and multi-hit 5* abilities actually will be less pronounced, but by then the good ones
will be r4 anyway, so it's a moot point.