In terms of DPS, this mod will still have a negative impact overall: Amprex and Synapse, who profit most from this mod, with Point Strike and Vital Sense and no fire rate mods installed will still gain -26.1% DPS vs normal body parts and -24.9% DPS vs heads from adding this mod to them, despite their individual shots dealing +15.5% damage vs normal body parts and +17.4% damage vs heads on average.
Therefore, the benefit of this mod is not DPS gain, but increased ammo efficiency, especially on weapons with high rate of fire (Synapse, Amprex, Soma), in which cases ammo is wasted during the reaction time between the target dying from the damage and the player suppressing their fire after that, on top of the fewer shots needed to kill the target due to the critical chance bonus.
It can also be beneficial to use Critical Delay for increased reliability of critical hits, when used with Tonkor it takes critical chance from 87.5% to 104%, making sure all mobs will always be hit with a critical hit rather than hitting for critical damage most of the time.
It benefits on slow-firing crit-based weapons such as the Vectis (particularly so since its single fire nature minimizes any effect on fire rate) or Tonkor, but is not effective on charge weapons such as Lanka or Bows, because it increases their charge time.
In almost all cases the +90% damage boost of a maxed elemental mod will increase both single-shot damage and overall DPS over that of critical delay, due to elemental mods stacking multiplicatively with base damage and critical hits. This comes at the minor cost of 2 extra drain, and depending on the element chosen may be more or less effective against the particular faction the user is facing.
Users may find that equipping this mod on the Grakata to be very effective, as the reduction in fire rate can reduce recoil while increasing critical chance.
Mods that improve fire rate can be used to offset the penalty if desired. This is particularly prudent for weapons that fire slowly, as with the addition of a high-ranked Critical Delay they may fire too slowly for the player to effectively dispatch foes. A fully ranked Shred in particular can almost completely negate the fire rate penalty while giving the rifle Punch Through.
Fixed in-game stats for weapons that fire continuously (Flux, Synapse etc). Made fire-rate mods actually increase damage output and ammo consumption rate for these weapons (not only is this intuitively what you would expect it's important to maintain the balance for corrupted mods like Critical Delay).