I've seen people say that Dumas is on the same level as Data Adult Zahard, but I don't think this is a correct interpretation of the dialogue whatsoever.
Unlike Dumas' power, it is made clear that Baam doesn't have an accurate perception/gauge of Data Adult Zahard or the fraction of Urek's power he has seen. To him, the power he has seen from these two remains as incomprehensible in his mind. Dumas' power can be comprehended and resonates with him more because of that.
The previous dialogue outright states that Dumas doesn't compare to Data Zahard (and by extension probably to 10% FoD Urek as well, since both strengths are deemed as something he can't grasp). The most you could say here is that maybe the Rosario Ignition compares/comes close, but again, it should be taken with a grain of salt as Baam cannot gauge those guys properly and doesn't know what they can do. Needless to say, just because Rosario alone might compare, it doesn't mean that Dumas overall does so.
As for the scaling regarding Hidden Floor Urek, he should likely scale above Data Adult Zahard, since his power couldn't be copied properly and Data Zahard's could. HF Urek >/>> Data Adult Zahard >> Dumas (overall) > Current Yama > Boosted Kallavan would be my guess.
As for the Revolution Guardian, absolutely no idea. I don't think there's any metric we could use to feasibly scale him.