DoT damage ticks get overridden if they occur at the same time

Only one damage tick can be applied to a target at a given moment in time. Sometimes you can stagger the ticks and get multiple dots going at once, but certain ones simply can't coexist ever.
There appears to be some kind of priority to them, as the fire dot from khaz dagger always overrides lightning storm's lit dot, regardless of which is applied first.
This only applies to the damage ticks, as the secondary effects are still applied as far as I can tell (ice slow, lightning lower hit chance).

The issue names no files, tests, or entry points. Start by reproducing simultaneous damage-over-time ticks involving Khaz Dagger's fire effect and Lightning Storm's lit effect, then identify the relevant combat or spell logic; done means compatible damage ticks coexist without removing their separate secondary effects.