Good to hear but I'm afraid that build I posted is outdated by now.
On what game version are you playing? The april patch 1.0.1.8 brought some substantial changes for DEX-based and melee builds. DEX AP bonus for light weapons was reduced from 4% to 3%. 14 DEX + tabbis were enough to bring the attack cost down to 6 AP and Taste for Blood feat had the potential to reduce it further to 4 AP which is the current cap.
Now 14, 15 or even 16 DEX + tabbis equal 7 AP attacks and Taste for Blood offers no AP reduction anymore. That reduces the potential of 12 attacks within 50 AP down to 7 attacks which is a loss of more than 40%!
http://www.underrail.com/wiki/index.php?title=DexterityYou could ofcourse plan to increase DEX to 16 which when supplemented with eel sandwitch (+1 DEX temporary) is enough for 6 AP attacks (8 attacks per turn which is still a loss of 33% compared to before) but you'd have to shed off two stat points from CON rendering both Thick Skull and Survival Insincts unavailable. So I no longer recommend the CON route for knife fighters. Too bad you're in middle of a playthrough and there is no way to respec your build. I wish Styg would leave previous versions as an option in the "beta" tab in Steam game property. Some games like Europa Universalis 4 have this. More than once did a patch ruin my playthrough.
I haven't played with knifes since the nerf but it seems they are the weakest branch right now, becomming less suitable as a main weapon but merely as a support for special attacks like Cut Throat, Eviscerate or finishing a badly wounded enemy with Ripper crit bonus.
Something needs to happen to make knives attractive again. They have the best critical damage bonus of all melee weapons but that's by far not enough to compensate for how slow they became. There are faster than 12 base AP knives but they are too weak for combat. 11 AP TiChrome doesn't help in this matter. There is also -1 AP gain from the supersoldier drug but the components are too rare to make a regular use of it.
Maybe knives could get a feat for a special "Flurry" attack that does 3 attacks for the price of +50% more AP and reduced precision (same as Rapid Fire works for some firearms) but with 1 turn cooldown.
Back to how knifes are best played right now. There seems to be no way around 10 AGI and Blitz anymore. Fatal Throw was also nerfed to 18 AP refund only once per turn but at least it still offers net gain of 7 AP @17 DEX.
Best case scenario 1st turn: 50 base AP + 20 from adrenaline drug + 18 from Fatal Throw refund = 88 AP
2nd turn: 50 base AP + 20 from adrenaline drug + 20 from Blitz + 18 from Fatal Throw refund = 108 AP
That's enough to fit in a knife throw (11 AP) and 12 regular 6 AP attacks in the first round (83 AP) and in the second a throw + 16 attacks (107 AP). Sounds good but thanks to lightning punches unarmed can do 19 and 24 attacks (4 AP each) in the same scenario. SMGs have even more potential.