Are you really sure of this ?
I'm pretty sure damage doesn't stack, it really looks the same. But the area of effect would be nice if confirmed.
After some testing, I must say I have a hard time to notice any difference in the poison clouds area with or without quickness.
I tried with small numbers and grid and it seems a censer does a 2-3 squares of poison cloud per strike regardless of the bless
It's hard to tell with huge numbers because of the "fog" of war
They still move and strike faster which is never bad, but enough to justify it over better scales or other bless?