So there's a 1 per rest Summon 3x Shade item.
3 Shades vs. most things = things lose.
I've got it equipped on my tank PC on PotD. Any time a battle goes seriously south on me, I pop shades and quickly turn the tides. I've even had ONLY my tank left, summoned shades, and they clean up everything NP.
The Phantom summon Chanter gets is pretty good. But 3 shades basically spam stun a single target, or you can split them up and CC three targets for awhile. It's hard for most enemies to deal with just a single shade beating on them.
Shades themselves, and shadows, phantoms and the like are probably just overpowered themselves. They're easily the most difficult/frustrating part of the early game to face. They have crazy high deflection and high defenses, seem to have sneak attack, and they attack fast and interrupt a lot. And of course as many people have found out they like to teleport past melee and just KO your Aloth.