I think the OP is 100% correct in terms of how elemental surfaces work now being unrealistic. I also think that they are fine just the way they are.
Why?
Because IMO, gameplay trumps realism. I feel that the combat in D:OS is pretty solid right now. WAY more solid than most games in its genre. I actually have to think every fight, and the way elemental surfaces work are a big part of that.
Right now, a poison or fire surface is both a huge danger and potential asset. If they are changed so that you can just walk through them and only take damage once, they will become more of an annoyance than anything else. And all of the neat spells specifically designed to clear certain elemental surfaces like rain or tornado, will become near useless. I mean, if I'm only going to take 20 fire damage for walking through a massive field of fire...why would I waste my mage's turn on putting it out?
I think this would drastically change how the combat in D:OS works, and not for the better. It would shift closer to "traditional" RPG combat, where the fighter runs in, healer heals him, and mage sits back...with nothing really exciting. Not what I really want.
