Totems and collisions
Mob attacks that target your totems do not collide with them. Webs, frost blast... whatever. It looks like the totem is a friendly target for them.
This is particularly reinforced by the fact that your totems get healed by enemy Inspire.
The totem seems to also have a 100% dodge chance.
A spider lich could hit the totem in melee, probably due to chilling touch. So I guess that for some reason the totem is incorporeal.