Also you need to deal with the fact that I consider mystics and 3.33 r8 assassins as somewhat-balanced classes.
Yes, I know they have edge in PvP, but when it comes to assassins, the more people take part in PvP fight, the less useful assassins are becoming (or just more useless). Mystics stay only average.
I don't think that it's possible to nerf assassins without breaking the current balance or without any negative impact on the community (unhappy players and so on...). Regarding mystics, increasing Absorb Soul cooldown wouldn't be big nuisance, although I don't think that it's necessary and I think that it can stay as it is now, that's why it won't be changed.