They are split half and half by religion . Then they have same issues with clans as us . Somalia has two nations they have none and are under Amhara centric state from religion to language . They have alot going against them
Oromos are highly underestimated by Somalis for some reason. They will be the ones doing the assimilating if they want to since they hold the seat of Ethiopia with SR under their jurisdiction.
Y-DNA does make you Somali. If you do not have one of the 3 main haplogroups then you are not one. Language does not make one Somali and vice versa for Afaan Oromo.
Oromos simply do not assimilate unless it's done through the barrel of a gun. How'd you think some clans managed to assimilate them? It was due to raids, invasions or remnants of a migration which they were forcefully assimilated.