When I experienced that issue, my solution was to attack the portal briefly, then switch to a monster if the required damage was not yet met.
As a response to the suggestion - I would be more inclined to argue keeping Pest Control where it is in this regard. Reason being, obtaining void would imply possessing a combat skill adequate enough to both utilize the attire, and deal 50 damage per game. If acquired without combat aptitude, then it retains its value as vanity attire.
In short, if the goal is to obtain void for intention to use in combat, it shouldn't take long to acquire a combat skill apt enough to achieve the required damage for Pest Control points. I do however, support the time and effort you took to make a suggestion!