A jrpg that used dnd rules would be interestingyeah wtf why has no one made this yet
No. Closest you're going to get is something like Fire Emblem.
The older fire emblems will get you some of that feel, like the criminally under-rated FE: Path of Radiance and Radiant Dawn.
Disgaea to some extent as well. Those games are really over the top, but solid turn based strategy.
I wouldnt call path of radiance underrated