The answer you need is already inside Slashley's event encyclopedia here (https://docs.google.com/spreadsheets...gid=1090858479), or alternatively in the DMM wiki here (http://xn--hckqz0e9cygq471ahu9b.xn--...83%AB%E3%83%A0)
Quick answer: 80% without any light eidolons equipped, incremental bonus till 100% at max, so no, you don't actually lose enough to be outmatched by a random event eido.
Last but not least... general discussions thread please.
Lavendaddy do your thing.