Cantrip damage like acid shouldn't cause -2AC if it's not in the rulebook; Fire Bolt should not leave a fiery area with nothing to set on fire, Ray of Frost should only freeze the ground when there's liquid on it, etc. -- maybe rein in surface effects in general (debate)
I prefer the surface system for what it's worth. Right now they have some utility for setting up chain reactions with a well placed web or barrel, while with the Rules As Written (RAW) it's pretty much 'pick damage type' for a ranged attack.
Enjoy playing a wizard with concentration spells when too many things get surfaces they do not deserve
