Nah, I can believe in the arena defence conspiracy, but still reckon the souls business is just confirmation bias. It feels that way, but it always does when you get smashed in the soul opening. This of it this way with heroics. You only have a ~10% chance of getting a 4*. There are 3 of them in the rotation, so you've actually only got a 3% chance of getting just the 1 you want. If you want a 5*, then its a 1% chance to get either, so 0.5% chance of getting the one you want.
So to get redan specifically, with just heroics, is always going to be a reallly tough thing. better of amassing legendary and mythicals by far.