Knife, as in the old days, are pretty bad.
Although, at some point, it gets buffed because you could cutthroat easier with flashbang.
Imo, you should try making the end-game build first instead of going full blind run.
The easiest way to plan your character is just pick feats you want, then adjust your stats accordingly.
For the "non-primary" stats, you could Google Destroyor's steam guide for recommended "soft-cap".
I did knife+throwing before the flashbang buff, and it works quite nicely on Hard. Although Foundry is kinda annoying because there's monster which immune to crit, have high mechanical DT, and pretty high HP.
I recommend to put Hypertoxicity to kill it faster.
