Returning weaker?

Returning player after 3 months or so, bunch of new stuff and a new stat, fortitude. How important is it? I'm aaking bc I'm at 2060 gear and I had a low tier self sustain thing going for myself (Not a min-maxxer and I'm trying to force Dagger Primary and Bow secondary) that was okay, but now I go into Death's Abyss 1-star and I get one shot by the "I'll wipe you all" attack as well as the boss doing extreme damage on comparison to what it was before I stopped playing. What happened and is there anything I should do? I now have 3 piece phantom wolf and I'm still just getting wiped.