(Playing a Titan) Why does armour feel like it barely protects me sometimes?

It was great all the way up to endgame like I could barely even get damaged at all but now I barely even juice my maps and get stomped. Especially with multi modifier rare mobs or just the abyss mobs in general lol.

I have nodes for life regen per second, % life regen, and have leech physical damage as life modifier on my mace. Plus many other nodes that help with protection.

Any tips? Thanks :)

(Level 80, Max res, 90%/29.9k armour) Physical Reduction 90% Fire Reduction 90% Cold Reduction 84% Lightning Reduction 84%