I have yet to use a single barrel. Have not used terrain damage mechanics. I admit to using positioning, including height, but as far as I am concerned, if they can attack me from a roof, I can do the same to them.
There are choices you can make as to how to play the game, and I am not ready to write off everything that happens to step in part from DoS2 - I'll wait to see how it all balances out in the end.