During High Priest Venoxis's snake phase he spawns green oozes out for the ranged, I found a few spots out in the back where a healer or ranged can stand and NOT get any damage whatsoever.
Warning: you have to find the right spot b/c if you twitch around, you'll have to jump far away to avoid the damage since you're surrounded by the pools.
My theory on how/why works: the spot is a little mound and the pools spawn around the toon, not directly under. And the pools deal dmg to your feet, if you're in LOS of them, so when you stand on the right spot, they spawn above/bellow. And when they spawn on the side of your feet, the curvature of the little mound you're standing on helps to LOS to your feet.
Attatched are two screenshots, one of which makes it painfully obvious I'm not dead, but I should be http://i53.tinypic.com/54ac6s.jpg . 2nd is a clearer shot of where I'm actually standing http://i54.tinypic.com/2afd2lf.jpg.
Never tried this with 2 ranged at once, but I'd think they would need to be pretty much exactly on top of each other, else the pool will spawn on top of one person. Don't know if there's other spots near the door or near the walls that allow this either.