Bear in mind that for a late build fast attack character, the additional damage is not huge.
Base sword example, @ lvl 35, Ursine Silver Sword (avg Damage 415 +75% Crit Damage).
The naked character gets 477/892@5% fast and 874/1635@5% strong. Game presents this as 793DPS (I agree with the calculation of damage, but have some questions about how the 4 damage values are mixed to form the DPS value ~ it doesn't seem to follow a fixed rule I can identify).
With 3 Greater Red and a mix of fast attack and supporting Red Skills (9 Total) I get:
1819 DPS (1079/1805@15% and 1787/2548@5%). *possible to increase Crit Hit % using Assassin Gauntlets.
Dropping CAT into the next slot in place of one of 3 Alchemy/Sign skills I get:
1940 DPS (1162/2303@15%* and 1787/2548@5%*) (*Assassin Gauntlets give +10% Crit Hit, so 2070 DPS, 25% Fast and 15% Strong)
This is only +83 Damage, and +498 Crit Hit Damage (an average of +145 damage from a fast attack). These values are correct according to the calculations provided, and I am certainly seeing a few critical hits with higher than this average of 2303 damage (the base 415 is only an average, and the actual values range from 373 to 457).
Without resistance or armour the range of normal hit damage is 1044 and 1280, and the critical damage 2070 and 2536 for fast attacks. I am seeing values across this whole range during fights.
What +100% critical damage bonus doesn't give is a *doubling* of the damage on a critical attack. It is only 100% of the base sword damage added to the already enhanced damage value. Cat School is *really* useful in the early game when you cannot easily afford to spend 6+ skills and two slots in the combat tree to get +15 damage and +45 Critical damage (with a +6 CH %) ~ which is the functional equivalent. It is also essential to obtain the absolute maximum value possible in the end game... But for a mid-game hybrid build it is fairly weak if you have also focussed on fast sword skills (And also if you want higher resistances/protection levels).