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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.
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
This is not true, but keeps getting repeated. They never stacked. There was a bug that meant the dot would permanently stay on an object after that area stopped affecting that object, which meant they could accumulate from areas that no longer existed, but the areas did not stack.
We don't need to "deliberately" make things stack any more than we need to make things not stack. There is no default, the way duplicate effects are handled must be specified for each type of effect. There are currently 10 options, of which 3 are commonly used, a couple are rarely used, and the rest are a variety of special cases.