Haven't heard good things about RDM and 1h Prime Sword, sadly- I'm not saying its impossible, but RDM with all their unique self-buffs makes Naegling really hard to topple for raw WSD, and 1h weapons don't benefit from the added ODD/OTD effect nearly as much as 2h or ranged.
Sadly for your friend, I hear a lot more good things about RDM using the dagger than the 1h sword.