I have faced a problem with the dark retribution-IT'S INSANELY HARD TO USE WITHOUT A GOOD CTR, since whenever I drop it, the bullets go around everything, so why not have a circle around you when you're charging a bomb to show the blast radius/pull distance (on vortex bombs).
On a side note, 2 new UV type suggestion for bombs- priming time reduction and blast radius increase, the names are pretty self-explanatory
I'm mainly a swordsman, so this might by my nubishness at bombing speaking here, but nevertheless, discuss.
I'm mainly a bomber, and I think honestly you just have to get used to how your weapon works (as with all weapons). Swords have a certain hitbox, guns have a certain range, and bombs have their effect radius. All weapons have their own charge time and time of execution (attack speed for swords, attack speed and bullet speed for guns, fuse time for bombs). The indicator on most bombs is really just a guide - it shows the general area of effect, but it's occasionally a little off.
For haze bombs, it shows the radius of the resulting haze, but the actual blast damage radius is much smaller than what is shown on the bombs' 3*, 4*, and 5* versions.
For vortex bombs (as far as I can tell), it shows the radius of the initial damaging blast (the one that does like 8 damage). The actual radius of the pull is slightly smaller, I think. Of course, the actual finishing blast's radius is even smaller than that.
For shard bombs, I think the radius shows the area in which the bomb will deal maximum damage to a target by essentially unloading all 8 shards into that target. I've never used one of these bombs, but that's what I've been told by a friend who does use one from time to time.
Blast-style bombs' radii are accurate, as far as I know.
I haven't purchased the Expansion Mission, so I've never gotten the chance to see how Dark Retribution works, and I never studied them too closely when I saw them used in LD/ATH.
My point is, each bomb and the subject of its indicator is different, so if you plan on using a bomb then you kinda just have to get used to it.