To elaborate on the question, direct hit right now reminds me of an old problem with critical hit that dates back to world of warcraft years ago, where beyond a certain point; such as 33%, or maybe even 50%, getting additional critical hit rate didn't benefit the player as much because of how consistent you would critically hit.

FF14's current version of critical hit rate avoids this specific problem, ensuring it only gets stronger the more you get, and even benefits attacks guaranteed to crit already.

Direct hit on the other hand, might run into that 'softcap' problem eventually I described in that wow example. Apparently, with ~1700 DH on my RDM through deltascape savage + the occasional battlevoice from BRD, my DH rate was ~40% through fights.

I haven't taken any metric yet of how often I'm getting direct hits on my DRG with 2110 direct hit rate at this moment, but the core of my question is at what point should I not meld for direct hit, and just stick to crit/det melds to increase max possible damage instead?