when talking about performance you need to add details like: type of battle (field, raiding a village, siege defense, siege attack, etc); your PC config; game config; and so on.
Sieges, as a example, can have worse performance because all that pathfinding and siege equipment.
Also if you can track your PC performance numbers (CPU usage, RAM, disc, GPU and GPU memory, temperatures, etc) by using the resources monitor (or any other utility). I personally keep them on my second monitor while playing, so I can keep a eye on performance after patches. This way it is easier to change the game options and see the effect (not just the FPS generic number).