In multi mode, the same settings of Reverb/Delay are applied to all 16 channels. If you edit on a "single" within a multi-setup, those settings will be used for all other "singles" on that multi-setup. It's one per patch, if it's a multi-patch, its for the 16 parts...
I think that's changed with the TI line, that those settings are applied per part... That's the biggest limitation of the Virus, compared to the Novation's Supernova, for example. But if you record one part at a time you get all the voices and you can specify those settings for each. That's what I'd do
Cheers