Periodic Invulnerability is a cheap mechanic

Just ran into a rare in a map with Periodic Invulnerability. I sat around trying to damage him for a few minutes but can't, as the "periodic" part seems busted. Even if it was periodic and I could kill it, I'd still hate it. I hated this mechanic in D3 and in PoE1.

Proximal is also annoying.

making non-boss monsters invulnerable for any reason is annoying at best

Add Prowling Shades to the list. They have it built in.

Periodic definitely procs too quickly and often. Needs a longer cooldown or some kind of balance tweak.