How I see the "all one" thing is like this. If we see consciousness as one event, then our egos act as tuners with a lens to focus in on one aspect or "camera angle" of that event. It's a way of being able to roam around and interact with itself, if that makes sense? Consciousness experiencing itself. So in a sense I see it that we are outcroppings of the same consciousness and the ego aspects of our mind is what acts as a kind of sorter that makes that separation illusion occur. The ego is nor good or bad but functions accordingly. I think ego gets lumped in with self importance and I think they are very different beasts. The ego is nothing to transcend. Whereas self importance creates separation and ultimately a kind of dis ease state. It;s like if a cell in our body were to want to leave the rest of the body. May not be optimal for that cell.