I find a 3X9 is my "happy place".
An 11 speed cassette is going to have a useless 11T smallest cog to go with your 30-40-52 chain rings, so you are basically upgrading to a 10 speed.
Your RDER is already maxed out for chain wrap capacity and 1T shy of max cog size.
If you need lower gears, get a 9 speed "mountain" RDER so you can get a cassette with a larger "biggest" cog and a 12 or 13T smallest.