I agree the RNG is more brutal in this game than some others. 70% is like a leap of faith
It looks like flanking affects the target's defence rating which is used to calculate chance to hit. It's hard to compare functional probability but I feel like it increased my accuracy
Attack of opportunity only happens when some is trying to move out of your field of control. If they are walking around you to your back it won't trigger. Being vindictive boosts it's accuracy
