The last healers i did have in instanced content wouldn't even heal raid wide unavoidable aoe damage, there were too busy dpsing. I sure dont want to count on them to heal me after a fall. What about destroying hastily made barricades obstructing the way instead ? After all it makes sense that the mobs would want to block your path with whatever they can think of, and it is more in line with the green dps way of life.