Dont forget this is coming in 3 waves
first one is 20% against current numbers = new_resists
second wave in 2 months is another 20% reduction against new_resists = newer_resists
third wave sometime after that but not scheduled yet would be 20% against newer_resists to make the final_resists numbers.
This had great buy in from the community and overall the balancing should not impact as much as people think unless your botting.
TLDR; PVE will be fine.