Yes.
From what I can tell burns can stack, but ignites don't stack. The burn from herald of ash, ignite, searing totem, burning ground (From flame trap), and scorching ray do stack.
Also, from what I can tell, whether a source of a dot stacks with others from the same type is customizable by GGG on a per type level.
Also, interestingly enough, it looks like GGG needs to deliberately make them not stack, as evident from the rework of coldsnap (when it first came out, a spell cascasde of coldsnap had the over lapping damage areas stack, but then they fixed it, there was also a bug where while the graphic went away, the dot didn't). And how all the pods from toxic rain stack dots. But multiple caustic arrows splats don't.