I have created a character on all servers and attempted open world combat - I managed to get into combat with a player twice in PVP1 - in both instances, someone else attacked me.
I also managed to initiate combat with an NPC. Once another player initiated an attack, a circle formed in the open world, and I was able to click on a double-sword icon. From there I got a context menu that had a button to enter battle. I was able to enter the battle just like an Admiralty offer.
I also managed to initiate combat with an NPC two times. I was on the PVE server, I had initiated combat and waited for the timer to complete several loops. I left the combat area and allowed the timer to tick to 0, then disappear altogether. I then re-engaged once I was within range, and the very second I clicked attack I was loading into the battle. I tried to reproduce the successful attack but I was only able to reproduce it one time on PVP2. Both times I had gone quite some distance from the same NPC while keeping it within visual range. Once I returned I was able to attack successfully, but there was no timer I was instantly loading the battle.
I have another PC - I accessed my work machine today and it was not meeting the minimum specifications for achieving more than 2 frames per second. I was unable to attempt combat. I have convinced my superiors and they will allow me to install a graphics card for a test after work hours. Expect a result in around 24 hours.
I hope it is just my machine, but it feels odd being the only person to ever have this issue with relatively common hardware:
Windows 10 upgraded from 8
Dual Monitors
8350 AMD
GA78LMTUSB3 Gigabyte motherboard
8GB RAM (1333mhz)
Nvidia GTX 760
Totally modest but meets requirements = getting 35-50 fps.