Unlike the Restless Rot of S7’s Headhunting event, there’s not enough Spectral Ash to go around. It feels rather stingy by comparison, thus making it a tough decision how to spend them, since you acquire very few. With the Restless Rot, you didn’t feel guilty splurging on one or two witchpowers right away.
With how frequent we kill the event bosses, they need to yield way more Spectral Ash than currently and/or have them upgrade their corresponding power with each kill.
Side note: IMO, I found the headhunting events of s7 way more fun than this (and the most fun I had with a seasonal event).