When the skill says: The target gains -41% and -4% more each time it is hit. Does this -4% reduction only apply when you are hit by special skills or do tiles also count towards this reduction?
Tiles count as well. You can mouse over the target and it will show the cumulative effect after each tile or source of damage.
Just note it caps out at -64% (or is it 61%? 65%?). Either way there is a cap otherwise the defense would straight to 0 lol.