how to deal with the tardigrades in stonefang efficiently

I'd like to finish Stonefang but these big firebugs take like no damage and I'm hacking away for several minutes on the big ones until they die. I'm not even sure my weapon has enough durability to kill 2-3 of these. I've explored a little past Leechmonger in the swamp area of Valley of Defilement in hopes of finding a vendor that sells poison knifes or something but I haven't found anything and that area is very annoying in its own right. Any ideas?

im playing the OG version on a ps3 emulator btw so no online sadly