You might be right - you are the only one potentially reading this who was likely there. Ill just point out that while sometimes "reflexes" is the issue, sometimes its more an issue of recognition of what the new mechanic is asking you to do. Lets look at the bird-beam mechanic from E7(Iconoclasm). In normal mode there are 3 versions of this attack that get used through the fight. The first version has safe spots you can stand in. Getting there is reflexes(as is moving to the second safe spot after the first attack). Seeing the safe spots in time to move is recognition. Second pattern, there are no safe spots and now you have a debuff on you. If you read the debuff, it says that getting hit with the same color is bad. It also says that when you get hit it will change polarity. So again, moving in time to align with opposite color birds is in the reflexes(repeatedly as this wave tends to hit 3 or 4 times). Identifying your debuff and the ideal places to stand is back to recognition. Final pattern is no safe spot with debuff, and with a set of portals behind and alongside you so that youre getting blasted from the side just after the hit from the front. This pattern is all recognition. You have almost 10 seconds to get into position before the attack goes off, so quick movement isnt the issue. But mentally you have to note your debuff, identify a column with opposite birds, see which birds will be going into/coming out of which portals, remember that your debuff will flip after the first hit, then identify into a row where the correct birds will come out(in this case, the color of the buff you started with), and finally get into that correct square. Ive seen plenty of people who recognize and get into the right square within the first 2 seconds. Ive also seen more then enough who take most of 8 or 9 seconds to figure it out and are running into safety as the attack is going off(safe is safe, getting there earlier just makes it easier to go back to attacking). Then you have the group of people who just dont get it at all. They have probly a 50-50 chance of guessing a good square(more like 25% if they havent figured out the debuff at all) - and they die when theyre wrong.
So if the answer is that youre moving a little more slowly, the solution is to make sure that you know what you have to do so you can recognize the situation faster and give yourself as much reaction time as possible.