I think the surface/status effects are fine the way they are, but their application should be tweaked. It gives you some extra flexibility and imo the extra chaos and unpredictability it adds to combat is appealing to me, if sometimes frustrating.

I agree with above that the burning status shouldn't be applied by anything and everything that is on fire. I think that if you limit what will apply burning status the effect itself is fine.
The acid-effect is a little annoying from a logical perspective. Getting doused in acid and getting AC reduction is fine I think, but it just doesn't feel right to be made so vulnerable by simply stepping in the stuff. Similar to how being set on fire by everything just feels off.

In conclusion, I guess I agree with OP.