After checking card "Witch Hag's Curse" i've noticed a strange wording.
It's textbox contains next sentence: "Treat attached unit as though its printed textbox were blank (except for Traits ).
Angi'aries Action, on the other hand, doesn't have (except for Traits ), and can theoreticly blank Hero trait.

Any ideas how her Action properly works?

Severance said:

I thought of that too, but figured they made Angi's ability more powerful since you can only have 1 of her out there, so once per turn, whereas WHC you can have 3x and it's permanent (though subject to normal removal via support destruction, unit leaving play, etc.).

I'm pretty sure that Traits are always meant to be excluded. Making someone NOT a hero seems silly to me, but I'm sure we will get word on this one eventually if it was on purpose or not.