Increase damage taken stack?

[Nikkaszal]

Ahoy, quick question:

Do skills etc that have a "target takes x% more damage" effect stack? And if so, additively or multiplicatively?

Example: if I have the Haunt rune that increases all damage taken for the duration by 20%, and Pirahnas for 15%, and cold Zombie Dogs for 15%, how much increased damage is my target taking?

[Deleted]

think it's stacked additively

so if X skill does 100 dmg and you have Haunt rune it will then be 120 dmg, if we also add piranha it will be 135 and with zombie dog 150