a) In 5e, terrain conditions like elevated ground can give Advantage, but it is a DM's call. So Larian is not really bending the rules here.
b) the percentage to hit is a nice feature / much easier to evaluate. At best, there could be an option to show the rolls over AC.
Addendum for bad readers : I support the percentage presentation. It is only a visual choice : it does not change the rules.
This. I'm fine if they just show the math better, but the implementation is fine. You can see the dice rolls if you want to. I know I look at them all the time to see if I rolled a 2 or a 3. Because I do a lot.
