I got a suggestion on the Steam forums about whether accuracy-increasing skills would help.
In short, using Mark and increasing my chance to hit from 73/74 to 88/89 changed one of the 74->89% misses into a hit, but the other 74->89% miss was still a miss (as was the 73->88).
the next question is, will acc/dodge altering skills change this roll? i.e
80% > miss
80% > skill making you have 90% > ? would it be auto miss still or will the roll at least reroll to have a chance of hitting, thats my main concern about this
Excellent question! I did a quick test, I loaded my pre-arena fight save, took my guy to buy Mark and walked back and saved again. This did not seem to affect the initial pre-fight seed.
It'll take me some time to make a video, as I have something like 13 scenarios to demonstrate, and I should do at least 5 attempts rounds with each scenario, multiply that by 4 targets... it'll take a while.
I tested Mark. There is one enemy with a 73% chance to hit (Rex) and three with a 74% chance to hit. Mark boosts the chance to hit to 88/89%. Rex with the 88% chance to hit is still a miss. The Avid one is still a hit. The Cultured One at 89% is still a miss, but The Tenacious One at 89% changes to a hit. So I still don't know what's going on.
I reaffirmed that moving close to the targets does not change who I actually hit, and I also tried delaying my turn and having my mage teleport me to high ground. That also did not affect who I hit at all. That's right, even with two people moving before Sebille and moving her to a different location, it didn't affect my chance to hit at all.
I don't care what you have to say about XCOM - This is OBVIOUSLY not working properly.