Actually 1 extra damage per minute stacking turns into 6% extra damage stacking per minute when you reach the boss floor. They’re made to be minor debuffs at the beginning levels but they reach their hardest version every 6th level (every boss level)
but after the boss level, you go into a new place, get a new rank 1 version of the debuff, and rinse and repeat, only with more powers including an epic one (guaranteed after killing the boss).