That's odd, is it only in certain situations such as in combat, or in town as well?
I'll try to do some profiling and see if I can improve the performance. I know that it can get a bit rough if you repeatedly use call lighting updates via torches or the staircase to the slime boss(the fog plugin can stack up some lighting errors), but it should clear upon saving and reloading.
The skill system is still not quite complete either, as enemies are not locked to the grid while you are currently, and probably do need a bit of a speed drop to compensate in addition to reducing their aim range and attack speed. I'm working on a future update to give enemy difficulty and control choices, but it will be a bit of time before it's complete. That should also speed up/slow down combat in a way that will feel a bit more natural, which might help with the feeling of it being a bit slow or laggy if the issue is in the skill casting range/placement.