Spartacus is a smallish fandom anyway, but Spartacus/Varro is practically nonexistent. :( I did a search for you but as expected, I didn't find much.

http://archiveofourown.org/works/498674?view_adult=true

http://www.fanfiction.net/tv/Spartacus-Blood-and-Sand/10/2/0/1/0/39882/39883/0/0/1/0/

http://bloodandsandfic.livejournal.com/tag/pairing%3A%20spartacus%2Fvarro

It's always been a bit shocking to me that the pairing wasn't more popular...but, you never know what's going to catch on. *shrugs* Plus, Spartacus himself has never been overtly popular with the fandom, so maybe that has to do with it. Sorry, anon!