If you want to keep doing what you're doing but are OK with using a custom app instead of Rule Machine, this app was more or less designed for that purpose and should work: [RELEASE] Virtual Device Sync, but I think you'll have to let it re-create the virtual devices for you, so you'll lose whatever automations you may have set up with the existing ones. That being said, you should also be able to make a couple rules in RM per switch and make this work, but the app should be much easier.
But it seems like the best solution to me is to just not use virtual devices and instead use a driver that properly creates the child devices. Then you don't need virtual devices at all; the two channels of the "real" device are exposed as two separate Hubitat devices (grouped in the UI under the parent, but you can name them whatever you want). I don't have this particular switch and don't know if Hubitat will do that for you with any stock driver (guessing not if that didn't happen for you). If this is the switch you have, this community-created driver might work, however: [RELEASE] Fibaro FGS-222 Double Relay Switch - Driver [EDIT: This does not appear to create child devices as I incorrectly assumed.]
That definitely seems like the better way to do this to me.
