Not that I've been looking into your category (civil union), but I think it's pretty clear that the changes wrought by the recent DNU mean that foreigners who marry an Argentine are only eligible to apply for temporary residency now, and will only progress to permanent residency after the third year of this temporary residency (each year in between renewing the temporary residency by showing themselves to be still married). I did ask my lawyer about these changes to the rules for married people, and he confirmed that this is how it will work. It won't be any easier, surely, for someone in a civil union. (Whether civil union still counts for anything at all from a Migraciones point of view, I can't comment. It's obviously the threshold question for you.)
The DNU did specify that citizenship applications begun before the DNU came into effect could continue under the pre-DNU rules. But residency applications (whether temporary or permanent) fell outside this arrangement.
The DNU did specify that citizenship applications begun before the DNU came into effect could continue under the pre-DNU rules. But residency applications (whether temporary or permanent) fell outside this arrangement.