Which is why I don't like overhead joins. One is asking several pilots at once to all head for the same area, all at 2000ft AGL. Usually, one cannot spot all of those who are known (from the radio) to be arriving at the same time. In those conditions, I've aborted the join and came back later. But there isn't a solution to this, if several planes really do arrive at the same time. Not under VFR.
I often worry about this. Someone reports overhead join, descending on deadside, but you have no real way of knowing where they are if you're also approaching.
So far I've tended to wait until I think it's clear, but once I reported joining overhead and someone else did a few seconds later. Just carried on, but I did feel as though I was trusting to luck even though I was keeping a look-out. There are plenty of blind-spots even on a good visibility aircraft.