Actually, I'm getting similar.
When I face the dark fae boss and my mirror copies, if I use a speed boost first the opponent will then also speed boost, as expected - but then they get the next turn, not me.
So it goes like this:
- I take first turn
- dark fae takes next turn
- dark fae takes another turn
I had to stop using Arbiter and any speed booster, and that's solved it for me. Yes, I have all skills ready, but this is about how the game decides who takes a turn when speeds are equal. Normally I would have expected it to be in my favour, and it is for the first turn, but after then the game decides that dark fae has priority.
I haven't played dark fae enough to know if this is a normal mechanic or if it's a bug.