Event heroes deals more damage as their health go lower?

I notice a trend that during any event battle, esp at the last event level, bosses deal more damage as their health goes down. I am not talking about level progression, but rather single battle.
Initially they don’t hit that hard and then gradually they starts hitting like a brick.
Anyone notice this or is this placebo?

I don’t really know.
I usually settle board and heroes so i can give a great amount of damage right from the start, even more in a difficult battle.

So i pretty much never see them hit me at high health, and i can’t compare.