Idk what you mean by the whole game being balanced around weakpoint bullet/blight rounds.
Because you can clear things in a reasonable amount of time if people have good enough gear, even if there's no one to mark the enemies or give shifta-deband.
Also it depends on if the person not playing ranger knows what they're talking about, and not just to boss people around. There are people that tell rangers what to mark because they just want to help, not everyone is doing it just because they think they're so important that everyone has to listen to them.
If you want a single target skill that's somewhat similar I'd say go for the tech classes, they have the barta blot and zonde clad skills with two levels that accumulate a marker that detonates when you charge the tech of the appropriate element.
If the rangers can't decide on where to mark just continue attacking whatever part you were, because if they keep switching locations, they'll surely eventually move it back anyway.
Also weakpoint bullet recharges faster in NGS, where it's better to use them all at once, because of the damage they do on impact. That's also sometimes why the mark will be placed wrong because it can very easily hit a spot that doesn't have anything to lock onto if the enemy moves too much.