As of now, you can clear PK for those mixclass or non-mixclass with high Bright points.
Here's the solution on it.
http://5.34.178.95/rancp/home.php?page=pkreset - Hamachi Site
http://phazeran.ath.cx/rancp/home.php?page=pkreset - Main Site
http://phazeran.servegame.com/rancp/home.php?page=pkreset - Additional Backup site
You may choose in any of the sites above. All 3 above is the same.