Question about 1/1, damage reduction and Invincible

So I've heard from numerous friends that damage reduction skills apply to 1/1 attacks, such that when they get 1/1'd they're left with some hp and mp. For some reason though on my bishop Invincible doesn't seem to do that. If I get 1/1d I'm left at one, and the 25% damage reduction doesn't. work. Anyone know what I'm missing? Thanks.