I think you should raise the healths of monsters rather than giving damage reduction. because it will kill life steal that heals percentage of your damage such as pale order and champion point attribute etc.

And Second feedback. i think night market difficulty is really good you can take night market as a referance while adjusting difficulty and you could make master difficulty same as night market and vestige is a bit harder. night market right now is soloable but challenging if you give more salt to it and make it for vestige it would be a chef's kiss