When I updated my damage calc to include Olympia Eidolons, I noticed that Olympia Eidolon is about equal to 60% Gacha Eidolons. For my stats, when on-element. So they're no alternative to 100%+ Eidolons at all, sadly.
I'm not expecting the grind for them to be all that bad. I am guessing the same droprate as Magnas and the fights being about as difficult, so getting 3-Stars should be relatively fast and the final copy will take a while. Time will tell.