If you have a bunch of crit (such that it's better than det), a pentamelded crafted piece will likely beat out an i390.

I use Det as a baseline here. There's a Det entry in the damage formula that roughly / not precisely amounts to dmg = (damage before Det) * (100 + addedDet/166.66)%. In other words, each 166-185 points of Det (diminishing returns) increases your damage by 1%.

At 3000 INT, it takes 30 INT to add +1% to your damage, so we have let's say 180 Det = 30 INT, or 6 Det = 1 INT in a worse case. That means you wouldn't trade off 72 Det for any less than 12 INT.

Since DH is nearly always as-good-or-slightly-better than Det, and Crit also tends to be once you have enough of it (varies by job), you can use that 6:1 as a sane rule of thumb for questions like this.