Yes it was already nerfed specifically for this game mode yet the main problems remain.
> : Damaging a champion below 50% of their maximum health deals 20 − 60 (based on level) (+ 2 per Soul) (+ 25% bonus AD) (+ 15% AP) bonus Attack damage Ability power Adaptive damage and reaps 1 Soul. This cannot happen again for 45 seconds, resetting to 1.5 seconds on champion Damage rating takedown.
It can be proced way to easy if you have a poke comp in Aram. Getting low vs champions with long range damage abilities is a common occurence and was already disheartening before but now it has become more obnoxious with the added "execute" damage you receive once you drop below 50% of your health. This in itself is not the issue i have. It is the multitude of champions that proc it on you in a short duration. Quite often it is not just the case that one champion in the poke team has this mastery but rather half of the team. So they gain not only one soul they gain three from hitting you and don't you even dare die to them. Because then you will have a rapid refreshing of Dark harvest which will lead to more procs and dropped souls and even more damage increase...especially in later teamfights on this stage.
Either the reset time has to be increased so that this mastery procs less often or, which might ultimately be too harsh, you remove the reset on assists. Then again it is a "infinitely" scaling mastery, with the potential to be among Veigar Levels of threat. *_note hyperbole_