Yup as you found out, they defintily don’t double.
Good rule of thumb is that anything that gives the same Status Effect Symbol will over-write each other:
- JF will over-write the Burn Damage from Marjana, Azlar, Kelile, Nashgar and GM (and vice-versa)
- Sartana will over-write the Poison damage from Proteus & vice versa
- Rana will over-write the Sand Damage from Yunan, Jabber, Gafar, Hisan or Arman (or vice-versa)
Note tho that each of these Damage Over Time’s will stack with a different type.
The only exception to the “over-writing” rule is if the FIRST DoT is an “Undispellable” type (e.g. Jabberwock’s poison damage). This cannot be over-written (or cleansed).
A good guide to Status-Effects & DoT is linked below: