Chris:
Currently the "or" operator is not available in the DataExchange Query syntax. The more advanced queries can be done via "Query Builder" in portal.
DataExchange is somewhat procedural (true to RPC) so it focuses more on filtering down (AND) instead of filtering out (OR).
On a side note, if you're coming to the conference in May (http://www.dynamicchurchconference.com/conference) I’ll be speaking on the new RESTFul API and we will have a panel on the future of our APIs, where you can drill us with questions and tell us what features and needs you have for our APIs.
--Nick