Salaam!
Here's the thing I found out with Yerevan so far.
They expect to communicate with your fiancee. My emails go unanswered, and they'll reply to her within one day.
When we got the invitation letter, they asked for her email address, and only then did they actually send the invitation document and other information.
We did get an interview. Finally!
What she had to do is send them a completed copy of our DS-160, and make her case to get an interview date because our petition is expiring soon. USCIS puts 4 months on the petition, and the NVC ate up 2 months. Yerevan responded in less than one week after the NVC forwarded our case to them.
The free appointment slots are not up when you go through the AIS system to register your DS-160 and pay the MRV fee. They'll open up slots after your fiancee emails them (no phone and they only like to reply to fiancee).
Hopefully, that will change and you'll be able to schedule when you guys in the information--but be prepared for the stress.
From what I can gather, the NVC is mostly contractors. It's probably a safe bet they drag their feet and complain once they accumulate too much to do--so be prepared for any communication dealing with the NVC to be next to nothing. Their inquiry information does say to contact them if you have not received any word 6 weeks after USCIS sends their case to them. Make sure you do! The only communication was the K1_FTP (K1 forwarded to embassy)--and it will be a Rich Text File format. The only way I found out they received our case was through the inquiry system. They never sent any notice.
Message me with any questions you have. I'll do my best to respond as soon as I get them.
Make sure to scan your NOAs and keep good copies of everything. Once your case gets to the NVC make sure to start preparing everything you can (start now if you guys can). After the case makes it to Yerevan do your best to move on everything as fast as you can.
Good luck!!
-Will