50/50, its either you get the Rika drop or you don't. Yes its a big dump of stamina but since your chances of getting Rika on Out of Control X are the highest possible AND at such a high rate its more or less worth it, hence the point of unit farming.
And yeah, all of the G maps are like that. You either just have to do it multiple times to get the pattern down and make a strategy from it or you search for other people's runs of it and try to copy their deployments to the letter.