Well its small comfort to know I am not alone with this problem, I thought it was my rig not able to keep up.
This being the case I feel confident they are working on it because sieges are unplayable, feels like I am back playing Jedi Outcast on a windows 98 rig...I managed to hold on to my hard won first castle by turning graphics way down and reducing troop size to 300, but its still a pain.
Field battles are fine on high resolution at around 800 battle size with the occasional stutter, load screens in general are slow.
I have an AMD 8 core 3 ghz, 16gb Ram and a RX 580 card.