Awesome to see that you guys are trying it fix it on your own. These translation issues are the only major complain I have about the game.
Regarding "corrosion", what about "Säure"? Not a literate translation, but it still makes sense. I think the same translation was used in NW2, if I remember correctly
And I like the "Direkter Schaden" for raw damage. It goes also well with being the resualt of mental and kinda poison effects... Insects not so much, except they like to bury themself in the body and do their thing there (ugh).
"Wundschaden" for me is more off a damage over time effect like a bleeding.