I am getting about 11 from a 1080 and 16.5 from a 1080 TI.  Both are not overclocked.   With some overclocking, I get 12.5 for and 1080 and 17 on the TI.

I just switched to "restart on crash".  That's much better than the scheduler.

I do have stability problems with my nvidia cards.   I run them at the stock clock speed, but the miner still crashes a few times a day.  To take care of that I use the windows scheduler to start the miner every 10 minutes and to kill the previous task if it is still running.  I need to keep an eye on it in the task manager, because every now and then I get two tasks running and my cpd rate is halved.  All I do is kill one of the tasks and everything goes back to normal. 

All I changed in the config.txt is:

server = "coinsforall.io";
# server = "xpmforall.org";
port = "6666";
# Your XPM payout address
address = "....your XPM address here....";

on the coinsforall.io site, the same address in the settings and set the minimal payout to whatever you want.  I have mine at 10 XPM.  If you ever want to switch to xpmforall.org, just move the hash (#) from the one server = line to the other.

I have my payout set at 10 XPM and get several payouts a day without fail.   I am currently using coinsforall, but I also had no problems with xpmforall.

I had been mining Primecoin for a while up until I lost the space for my rigs about a year ago.   I now have a place that I can set them up again.   
I currently use r9-270s (4 cpd) and 280s(6 cpd)   
Anyway, I have two questions.   What are the preferred GPUs for Primecoin mining now, and is there any reason to use coinsforall over xpmforall?