You can use the Ghorkaal Teir'Dal Illusion Belt you received in the previous quest to search for the racks in safety, but if you destroy the racks within aggro range of any Ghorkaal Teir'Dal, they'll attack you. When you find the racks, right click and attack them.
Slay poisonspinners in search of poison. Note: Keep necromancers and cursespinners killed, as they share spawn locations with the poisonspinners.
Return to Heathryn (must cancel Ghorkaal Teir'Dal Illusion before she'll speak to you).