I went for Crit IV x3 + Crit III x 2 (39 Crit total)
Its only about 0.9 Dex behind the best melding option (Crit IV x 4 + Det IV) but should work out substantially cheaper. (To make up for this, you can gain an extra point of Dex if you switch to Wildwood Elezen!)
Although I still managed to break 5 Crit IV's on that first overmeld, so it wasn't that cheap... :(
I wouldn't spend too much melding any crafted gear at this moment in time though... as mentioned above, the new Crystal Tower will be out soon, which may have some good alternatives.