Why not? After all, Dragon was distressed by the possibility of Sabo killing Cobra. Sabo possesses a destructive power and is listed as one of the most powerful fruits in this category. He would also put all the kings of the nations in danger if he used his abilities to their fullest potential, since the Mera Mera fruit provides pure destruction and AOE. The same can be said for Karasu, since he is a Logia and Logias usually give a lot of AOE. So yes, the revolutionaries are capable of holding off the two admirals even if both groups are restricted. It's not like all of the abilities of the admirals and revolutionaries cannot be used, some that are not as destructive can still be used, such as Green Bull's branches that pierce the opponent, for example.