I think a stack limit of 10 might be going a bit far, they could just reduce the “increased damage taken per stack” from 8% to 2% & that would have a massive impact on the top end damage. Assuming I’ve got my maths right (which is always a bit of a risky asusmption), dropping the damage buff per stack from 8% to 2% would decrease the damage by 33.3% @ 10 stacks, 66.7% @ 100 stacks, 70.6% @ 200 stacks. If you drop it to 1% then the damage falls by 38.9% @ 10 stacks, 77.8% @ 100 stacks, 82.4% @ 200 stacks.
So the damage reduction asymptotically approaches the reduction in the % as you approach infinite stacks. Dropping it to 4% would give you 1/2 the damage as you approach infinite stacks compared to the current 8%. Dropping to 2% would give you 1/4 the damage as you approach infinite stacks compared to the current 8%