This is a bit of a problem with them showing a % to hit in general, while there technically is always a % chance to roll a number high enough to hit, the actual chance to hit is all completely random. You could have a 1% chance to hit and get stupid lucky and roll a 20, or the % to hit could say you have a 99% chance to hit and then you miss 3 times in a row because you got bad rolls. It's all completely random and showing a % chance to hit makes it feel like you should be hitting more often, all you can really do is stack the deck in your favor by getting advantage from high ground or other skills and hoping lady luck is with you.
As far as I am aware the currently displayed hit chances are accurate and the dice are not weighted in any direction, although they are considering weighting them in the player's favor in future. If they do that, I would rather have a difficulty option with non weighted dice, since I am not a fan of weighting to begin with. The human mind is notoriously bad at grasping probability, there are a lot of studies on this. So even if the hit chance is perfectly accurate, people will "feel" it is wrong, because our grasp of probability as a species is flawed. If you wish to read up on the subject,
here is an example of a very simple puzzle to which most humans will choose incorrectly, even though pigeons will choose the correct answer.
Here is another paper on the topic. Game designers are also well aware of this, the probability of hitting is
skewed in the player's favor in XCOM for example. My favorite example though is probably this talk given by Tim Cain, at 25 minutes into
this video.
