Enemy Critical Hit Rate
Enemy critical hit rate is a merit category available to all jobs. It can be merited a total of 5 times. Each merit upgrade grants a 1% decrease in the rate of critical hits by enemies against the player. It costs 15 merits to fully upgrade (1>2>3>4>5).
This is typically merited by general melee. Tanks are well served by this (especially PLD), as are career casters.
Enemy Critical Hit rate seems to be calculated approximately the same as Player Critical Hit Rate, but using the Enemy's DEX and the Player's AGI. This means that, in situations where the Player has a large AGI bonus like Abyssea, the Enemy's critical hit rate is at the 5% unmeritted Critical Hit Rate minimum. Merit points, Equipment, and Job Traits can further reduce this, but it appears to have a 1% minimum.
Using this logic, it is difficult to justify capping this category. Even in normal situations against monsters with a higher level than you, Enemy Critical Hit Rate is still fairly low due to the nature of the DEX-AGI Critical Hit Rate relationship.