So testings been done and at 150 piety, dia/bio2 does like 60+ damage ticks, and poison 2 does like 100.
They generally last 30-60 seconds.
How often do they tick? if they ticked at 5 seconds then they're pretty much useless in any situation other than top level NMs where you can't just straight up banish/scourge for 400+ damage.
if it's every 3 seconds then it would be great on anything that took a while to kill.