This refactoring from cursor on a dblink'ed Oracle table OK?
Joins across database links can lead to sub-optimal execution plans as Oracle doesn't have all the information available about both sites. Queries across db links can (and do) perform just fine when joined to local tables though. 

If writing a new query with local and remote tables I'd start joining it all together (set-based) then only break it into separate queries if performance is unacceptable and other tuning hasn't worked.

Given your query is just a simple minus with no joins to the remote site, I would expect the refactored set-based approach to be quicker. Make sure you test it though!