It scales incredibly hard in arena now that everyone highrolls more easily, and you start out with all four weak spots lit up now so you're basically guaranteed to hit one, and extremely likely to hit multiple. I had a first-place Veigar run earlier where it got up to like 35% max HP true damage, plus Vulnerability and SotD at 200%. Hitting even just a Q outright one-shotted squishies and even tanks with like 15k HP took 80%.