So... do you really think you were doing it right?
Sorry this is a little harsh, but how do you get anywhere near 100 people before realizing the approach must be horribly flawed, and devising and implementing a better one? Surely it behooves you to not waste your employer's time, your own time, and the time of all those people you're interviewing (mostly pointlessly).
These were 25 minute phone screens for candidates that had been sourced by recruiting, a few years ago at a company that was going through hyper-growth (hiring hundreds of engineers in a year). Phone screening several dozen people for 2-4 eventual hires doesn't feel too inefficient to me.
Sorry this is a little harsh, but how do you get anywhere near 100 people before realizing the approach must be horribly flawed, and devising and implementing a better one? Surely it behooves you to not waste your employer's time, your own time, and the time of all those people you're interviewing (mostly pointlessly).