However, to be fair I had decent gear and used

backstab, trip, bind legs (with mixed success),
knockout poison (along with blackjack),
Grease weapon,
and Neurotoxin

and engineered a situation allowing me to take out a group of three that easily could have perma-lagged my character.

Migra never purchased his poisons (Outlander applicant), but instead concocted poisons from the huge assortment of poison ingredients that can easily be found lying around on the ground. I deleted Migra only because leveling solo as a thief absolutely stunk.

Poisoners are hampered more by the plenitude of poison-resistant mobs and one's creativity than by the cost of poisons or their effectiveness in pk. I'd play another poisoner in a heartbeat.