The current recommendation is to use multiple notifications and conditional logic or ensuring that all fields that have merge tags in the send to, bcc, or cc settings are set to required.
I think it would be much more intuitive (and you wouldn’t need to maintain 2 separate notifications) if GravityForms could handle the following in the TO, BCC or CC field: test@test.com,{MergeTag} where {MergeTag} may be blank.