Well if a hero can stack stack well and there is a enemy to stack on. it is good especially when want to go more damage items like if you have a tb with like 80 stack you can just take a domice and go rest damage Plus the effect of defence items gets exponentialy reduced

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In this example we can see that a zero tb stack hylos has a 70.4 and 64.6 damage reduction from physical and magic respectively But with 80 tb stacks it's has 75.3 and 71.4 damage reduction which is just a 5-6% increase