Rather too many people here getting frothy over changes from core 5e rules. Larian do their own version of 5e rules. Elemental surfaces are fun, make the map layout and positioning absolutely crucial, and allow for much more tactical play. Some people get hung up on minute differences from 5e: maybe enjoy the game as it is, if it doesn't work in the game, then critique it in those terms. 5e isn't a bible and it's not useful to be fundamentalist.
Yeah im going to go out on a limb here and say you are familiar with 5E rules.
For people who have experience with 5e they know certain things are op if given away to easy in 5e. Let me give you an example. In 5e very rare weapons will give you +3 to hit, and that is really powerful. While advantage is considered to be a +5 to the skill. So giving out a +5 to everyone above you, or behind you is really powerful in 5e rules. It's actually game breaking.
Now think of what that means. In 5e someone having advantage on an attack against you is the same as you having -5 to your armor. Lets say you have 17 armor class a good AC for a low level fighter. You now have effectively 12 ac considered low for even a casting in 5e. With 5e you always hit on a 20, and always miss on a 1 no matter the AC, and tie goes to the attacker. So with 17 ac for every 20 attack you will be hit 4 times. With the person attacking you having advantage you will take 9 attacks every twenty.
As you can see it might not seem like a big deal, but it makes being tanky much harder when you give away advantage.
In short you have to be careful what changes you make to the 5e system as it's easy to break, and in turn break your game balance.
