Is limit break not a thing?

[RiyahArp]

...

Let me get this straight. You think a 9,000 potency attack is less effective on a boss with... more HP?

Yes. It probably is better just to use caster LB during his add phase. The thing about a melee LB is that it's virtually never USEFUL; all it does is kill the boss very slightly faster, and with shinryu's huge HP, it kills him barely any faster. A healer LB3 though generally is far more useful as it will save a lot of time if used effectively by preventing a wipe, and a caster LB can be used to shorten an add phase. Tank LBs have very specific and rare uses, in which you HAVE to use them to survive. But melee LB can usually be ignored because if you are doing it ok, it's just a bonus of ten seconds in a run.

By the time most people use melee lb, they could just keep on doing what they are doing and the boss ends up dead anyways. It actually gets less useful the higher your dps is, and really only is vital in PvP imo.