While not as good as poison, a Pixie swatter does pretty good against them when they swarm (and can even collect you a few thought threads if you stand at intersections to fight the corrupteds, and collect the other type as collateral damage).
Any weapon with whirlwind and life leech can do pretty good, if you can get the damage type to fit.
I've been using a Radiant Scimitar that has no SSI, but DI in the high 30s and all 3 leeches better than the soul seeker. Add in Consecrate weapon, and it's possible to spam Whirlwind attack and rarely run out of mana, even on a character with no Med or focus.