Remember, the ones who know that are base Saiyans, and thus would instead hit 600 million (30 mil x 20 = 30 mil x 10 x 2; 30 mil x 10 = 300 mil; 300 mil x 2 = 600 mil. Still curb-stompable, at least individually. And for the one at 2.8 billion...I'm actually confused there. That would have the Oozaru at 140,000,000. That's the base power cap of a standard Super Saiyan as an Oozaru, and none of those have existed since the Clan system was formalized -- they get trained to mastery literally immediately. Plus, those aren't the ones you need to watch anyway. But, if somebody rebelled by going Super Saiyan, trained their base to 70 mil, turned Oozaru, and used the Kaio-Ken...their effective strength would still only be 1.4 billion, which a Super Saiyan 2 would effortlessly evade and a FPSSJ could get around as well if they knew the Kaio-Ken (that's your Dad's job at the moment, by the way. In the system of Lords, he is the designated Oozaru Suppression System). That said, if a fight that bad breaks out, the Masquerade has fallen, an Oozaru is splashing its presence all over the neighboring star clusters, and every Super Saiyan on Garenhuld is straining to reach SSJ2 anyway, because their cover is blown.
So yeah. Oozarus with Kaio-Ken training? Carefully watched.