It should be prioritizedbut shouldn't be mindlessly stacked.

You should only stack enough to approach a 33% crit. I've observed 24-29% crit rates at 542 crit.

Effective Crit rates expressed as fractions(%):

1/10(10%), 1/9(11.1), 1/8(12.5), 1/7(14.2), 1/6(16.7), 1/5(20), 1/4(25), 1/3(33.3), 1/2(50%)

As you can see it's ever increasing diminishing gains, and also until you move from 1/5 -> 1/4 rate or 1/4 -> 1/3 rate you can only realistically expect to achieve the lower rate of the two, since your actual crit rate will vary wildly in between the two from encounter to encounter.

Now take into consideration the stat points sacrificed to crit (e.g det, pie) and the MND abandoned in favor of crafted gear if it's being used.

@OP, you should start taking crit off and see how it drops chances are it's not going to drop noticeably until you are around 570 or so.